Annual epidemiological commentary: Gram-negative, MRSA, MSSA bacteraemia and C. difficile infections, up to and including financial year 2023 to 2024
Updated 26 September 2024
Applies to England
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Main points
The main messages of this report are:
- the overall incidence rate of Escherichia coli (E. coli) bacteraemia increased between financial year (FY) 2020 to 2021 and FY 2023 to 2024; FY 2022 to 2023 to FY 2023 to 2024 saw its largest annual increase since the beginning of surveillance, driven primarily by community-onset cases, which represented 80.7% of cases in FY 2023 to 2024
- Klebsiella spp. bacteraemia rates have been increasing year-on-year since the beginning of surveillance; FY 2023 to 2024 saw the greatest single year increase of 10.6% in rate, driven predominantly by community-onset cases
- Pseudomonas aeruginosa (P. aeruginosa) bacteraemia rates remained stable with an overall rate of 7.8 per 100,000 population, and a hospital-onset rate of 4.8 per 100,000 bed-days in FY 2023 to 2024
- methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia rates in FY 2023 to 2024 have increased incrementally by 14.3% (from FY 2019 to 2020) after a sustained period of stability, with rates reaching levels seen in FY 2013 to 2014
- the overall methicillin-sensitive Staphylococcus aureus (MSSA) bacteraemia rate exceeded pre-COVID-19-pandemic levels, reaching 23.5 cases per 100,000 population, an 8.3% increase; recent increases have been driven by an increase in the rate of community-onset cases
- Clostridioides difficile infection (CDI) cases have shifted to an upward trajectory since FY 2020 to 2021, contrasting patterns seen in early years of surveillance as cases increased by 33% between FY 2020 to 2021 and FY 2023 to 2024; this marks the highest overall case rate since FY 2011 to 2012, driven by recent increases in both hospital-onset and community-onset CDI cases
- minority ethnic groups, namely Black and Asian ethnic groups, showed the greatest incidence in the 3 Gram-negative bloodstream infections (GNBSIs, namely P. aeruginosa, E. coli, and Klebsiella .spp) as well as MRSA, in contrast to the White ethnic group, where MSSA and CDI had the greatest incidence; age-standardised incidence rates varied significantly, with some ethnic groups experiencing rates 2.6 to 4.1 times higher than others
- the case fatality rate decreased across all collections between FY 2022 to 2023 and FY 2023 to 2024, while the mortality rate remained relatively stable, except for MSSA where it decreased by 5.6%
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Epidemiological analysis of Gram-negative organisms: Escherichia coli bacteraemia
Total reports
A total of 42,224 cases of E. coli bacteraemia were reported by NHS acute trusts in England in FY 2023 to 2024. Of which, 8,155 (19.3%) were hospital-onset (HO) cases. The total number of cases reported in FY 2023 to 2024 increased by 8.9% compared to FY 2022 to 2023 (n=38,758), marking the largest annual increase since E. coli bacteraemia surveillance started (FY 2012 to 2013). From FY 2012 to 2013 cases have increased overall by 30.7% (n=32,309) and the incidence rate increased from 60.4 to 73.8 cases per 100,000 population (Figure 1). Despite not quite reaching FY 2019 to 2020 levels, this most recent FY sees overall counts and rates of E. coli bacteraemia very nearly back to pre-pandemic levels.
Figure 1. Trends in the rate of E. coli bacteraemia, England, by financial year: April 2012 to March 2024
Hospital and community-onset cases
Community-onset (CO) case rates (rates reported per 100,000 population) increased year-on-year from 46.3 to 63.6 between FY 2012 to 2013 and FY 2018 to 2019. Following this increase, CO rates for the first time declined between FY 2019 to 2020 and FY 2020 to 2021, reaching 53.7, coinciding with the beginning of the COVID-19 pandemic, and have since increased to 59.5 in FY 2023 to 2024. This increase was also reflected in episode counts, with 34,069 CO cases reported in FY 2023 to 2024, just below the counts seen before the pandemic.
In contrast, the rate (cases per 100,000 overnight bed-days) of E. coli hospital-onset cases was relatively stable at around 22.0 between FY 2012 to 2013 and FY 2018 to 2019 apart from a temporary decrease to 21.1 in FY 2014 to 2015 (Table 1). Rates continued to increase from FY 2018 to 2019 to FY 2020 to 2021 (22.1 to 23.6), then declined to 21.5 the following year, but have steadily increased since, reaching 22.7 in FY 2023 to 2024.
Table 1. E. coli bacteraemia counts and rates, England, by financial year: April 2012 to March 2024
| Financial year [note 1] | Mid-year population estimate [note 2] | All reported cases | Rate (all reported cases per 100,000 population) | Total bed-days | Hospital-onset cases | Rate (hospital-onset per 100,000 bed-days) | Community-onset cases | Rate (Community-onset cases per 100,000 population) |
|---|---|---|---|---|---|---|---|---|
| 2012 to 2013 | 53,475,357 | 32,309 | 60.4 | 34,633,855 | 7,552 | 21.8 | 24,757 | 46.3 |
| 2013 to 2014 | 53,976,973 | 34,286 | 63.5 | 34,514,871 | 7,558 | 21.9 | 26,728 | 49.5 |
| 2014 to 2015 | 54,432,437 | 35,822 | 65.8 | 34,972,728 | 7,381 | 21.1 | 28,441 | 52.3 |
| 2015 to 2016 | 55,018,883 | 38,313 | 69.6 | 34,752,604 | 7,744 | 22.3 | 30,569 | 55.6 |
| 2016 to 2017 | 55,240,934 | 40,682 | 73.6 | 35,148,014 | 7,888 | 22.4 | 32,794 | 59.4 |
| 2017 to 2018 | 55,707,642 | 41,140 | 73.8 | 34,903,075 | 7,683 | 22.0 | 33,457 | 60.1 |
| 2018 to 2019 | 56,053,563 | 43,284 | 77.2 | 34,538,184 | 7,630 | 22.1 | 35,654 | 63.6 |
| 2019 to 2020 | 56,468,265 | 43,400 | 76.9 | 34,637,156 | 7,839 | 22.6 | 35,561 | 63.0 |
| 2020 to 2021 | 56,434,900 | 36,804 | 65.2 | 27,628,155 | 6,525 | 23.6 | 30,279 | 53.7 |
| 2021 to 2022 | 56,690,879 | 38,037 | 67.1 | 32,905,086 | 7,081 | 21.5 | 30,956 | 54.6 |
| 2022 to 2023 | 57,106,398 | 38,758 | 67.9 | 35,490,766 | 7,873 | 22.2 | 30,885 | 54.1 |
| 2023 to 2024 | 57,223,954 | 42,224 | 73.8 | 35,991,392 | 8,155 | 22.7 | 34,069 | 59.5 |
Note 1: financial year from April to March of the following year.
Note 2: mid-year population estimates for 2023 and 2024 were unavailable at time of publication and so population data for January to December 2022 was used as a proxy/
Figure 2. Monthly onset counts of E. coli bacteraemia by onset of infection, England, by financial year: April 2012 to March 2024
Prior trust exposure
In comparison to FY 2019 to 2020, FY 2023 to 2024 saw an increase in the total count of hospital-onset healthcare associated (HOHA) E. coli counts from 7,839 to 8,155, with the incidence rate remaining stable, 22.6 to 22.7 cases per 100,000 bed-days. Contributing factors include a large drop in bed-days at the start of COVID-19, which has slowly increased in subsequent years surpassing figures seen prior to the pandemic.
Over the same period, both the count and rate of community-onset healthcare associated (COHA) E. coli bacteraemia counts increased by 7.4% (from 5,552 to 5,963) and rates increased 4.0% (from 14.4 to 15.0 cases per 100,000 overnight bed-days and day admissions), respectively.
The largest increases were seen in both the counts and rates of community-onset community associated (COCA) cases, for the same period, from 24,355 to 27,983 cases (an increase of 14.9%) and from 43.1 to 48.9 (an increase of 13.5%) cases per 100,000 population, respectively (Table S8).
Caution is advised in the interpretation of the data as the number reported with no information fell from 5,152 in FY 2019 to 2020 to 28 in FY 2023 to 2024. This was due to the fields being mandated from late 2019.
Figure 3. Proportion of prior trust exposure cases, by financial year, April 2019 to March 2024 in England
Age and sex distribution
In FY 2012 to 2013, sex or age was unknown for 815 cases (2.5%), versus 34 cases (<1%) in FY 2023 to 2024. Figure 4 compares the age and sex distribution of E. coli cases in FY 2012 to 2013 versus FY 2023 to 2024. Broadly, the distribution of cases was similar across both periods. The greatest burden of infection remains in the adults aged 45 years and over; within this demographic, both sexes in the 75 to 84 years age group have the highest proportion of cases, comprising 16.1% of male and 14.1% of female total cases (FY 2023 to 2024), respectively.
The percentage distribution of cases amongst males and females were similar across age groups, except in those aged 15 to 44 years, where cases were approximately 2.8 times higher in females compared to males in both presented financial years. For all age and sex analyses, cases for which the sex or age was missing or reported as “unknown” were excluded.
Figure 4. Age and sex distribution of E. coli bacteraemia by percentage of cases, England, by financial years: April 2012 to March 2013 and April 2023 to March 2024
The incidence rate increased in most age groups, for both sexes between FY 2012 to 2013 and FY 2023 to 2024.
In FY 2023 to 2024, both males and females had the highest rates among individuals aged 85 years and over at 854.0 and 569.9 cases per 100,000 population, respectively. In this period, the rate ratio between men and woman consistently increased with age in all those age groups containing individuals aged 45 years and over. This was also consistent with FY 2012 to 2013.
Compared to the last financial year, FY 2023 to 2024 displayed a slight decline in infection rates for both sexes in age groups under 1s and in males in the 15 to 44 age group and an increase in rates in those aged over 45 years.
In the last 3-year period post-pandemic (from April 2021 to March 2024), the rate in males aged 85 years and over increased by 6.4% from 802.8 to 854.0 cases per 100,000 population. The rate among those aged 75 to 84 years increased by 8.7%, from 367.5 to 399.4 cases per 100,000 population.
During the same post-pandemic period, increases were also observed in females, in the 85 years and over age group, an increase of 12.0% was observed, rising from 508.7 to 569.9 cases per 100,000 population. Similarly, the 75 to 84 age group displayed an increase of 11.4% since FY 2021 to 2022 (263.2 to 293.3).
All other age groups showed varying degrees of fluctuation but remained relatively low (less than 200.0 cases per 100,000 population) in FY 2023 to 2024.
Figure 5. Trends in age group and sex rates per 100,000 population of E. coli bacteraemia cases, England, by financial year: April 2012 to March 2024
The rates of E. coli bacteraemia broadly increased between FY 2012 to 2013 and FY 2018 to 2019. This was then followed by a large decline between the April 2020 and March 2021 period due to the pandemic. In FY 2023 to 2024, there was an increase in rate in most age groups and in both sexes. The highest increase in rate, when compared to FY 2022 to 2023, was in both males (12.8%) and females (13.3%) aged 75 to 84 years. This was followed by those aged 85 years and over, with increases of 6.8% in males and 12.8% in females.
Trends by ethnicity
In FY 2023 to 2024, the observed incidence rate of E. coli bacteraemia was highest in the White ethnic group (76.8 cases per 100,000 population), followed by the Asian and Black ethnic groups (51.4 and 46.2 cases per 100,000 population, respectively). It was lowest in the Other and Mixed ethnic groups (19.4 and 19.2 cases per 100,000 population, respectively).
The age-standardised incidence rate saw the highest incidence rates in the Asian and Black ethnic groups (107.9 and 86.6 cases per 100,000 population, respectively) versus the White ethnic group (71.0 cases per 100,000 population). Rates in the Asian and Black ethnic groups rose sharply year-on-year from FY 2020 to 2021.
Figure 6. E. coli bacteraemia rate by ethnicity, England, by financial year: April 2018 and March 2024
Note 1: shaded bands indicate 95% confidence intervals.
Note 2: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Trends by deprivation
In FY 2023 to 2024, 82.9 cases occurred per 100,000 people living in the 20% most deprived areas versus 67.5 cases per 100,000 people living in the 20% least deprived areas. The observed incidence rate of E. coli bacteraemia increased with deprivation.
The variation in age-standardised incidence rates of E. coli was much greater or lower than that observed (111.4 and 55.9 cases per 100,000 population) in the 20% most or 20% least deprived areas, respectively, suggesting the risk is almost doubled between these 2 groups. We also note the gap between the various deprivation levels are much wider for age standardised data even though the ranking does not necessarily change.
Figure 7 and Table 13 in the accompanying data spreadsheet show the incidence of E. coli bacteraemia by index of multiple deprivation (IMD) level between April 2018 and March 2024.
Figure 7. E. coli bacteraemia rate by deprivation, England, by financial year: April 2018 to March 2024
Note 1: shaded bands indicate 95% confidence intervals.
Note 2: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
All groups have seen increases in age-standardised rates in the last financial year with the largest differences seen in the more deprived levels. There has been a consistent ordering of age-standardised E. coli by increasing deprivation since April 2018.
Seasonal trends in E. coli bacteraemia
Seasonality was assessed as the number of cases each quarter as a percentage of total cases for the financial year. This analysis was performed separately for hospital-onset and community-onset cases. In general, community-onset E. coli cases peak in the July to September quarter of every year, a trend that has not changed since April 2012. Historically, there was much less seasonal variation in hospital-onset E. coli cases. However, in FY 2020 to 2021, hospital-onset E. coli cases peaked in October to December 2020 and January 2021 to March 2021. This was compared with previous years, where it peaked in the July to September quarter. These variations to increases occurred during the second wave of COVID-19.
Primary focus of E. coli bacteraemia
The provision of data on the most likely primary focus of E. coli infection information is voluntary. The percentage of cases where this information has been provided has declined over time from 85.5% (n=27,610) in FY 2012 to 2013 to 51.6% (n=21,788) in FY 2023 to 2024 (Table 2), an 18.1% increase versus FY 2022 to 2023 (n=18,444).
Of cases with a reported primary focus of infection, urinary tract has consistently been the most frequent primary focus for E. coli bacteraemia cases. In FY 2012 to 2013 48.9% of cases reported a most likely primary focus of urinary tract, and by FY 2023 to 2024,45.0% (n=9,810). Hepatobiliary as a primary focus has slightly increased between FY 2012 to 2013 and FY 2023 to 2024 from 13.6% to 15.4%. The percentage of records for which the primary focus was reported as unknown has decreased from 20.2% in FY 2012 to 2013 to 18.7% in FY 2023 to 2024. All other reported primary focus rates have remained relatively low between FY 2012 to 2013 and FY 2023 to 2024.
Table 2. E. coli bacteraemia counts and rates by primary focus of bacteraemia, England, by financial year: April 2012 to March 2024
| Financial year [note 1] | Total E. coli reported | Primary focus ascertained: n | Primary focus ascertained: (%) | Gastro-intestinal: n [note 2] | Gastro-intestinal: (%) [note 2] | Hepatobiliary: n | Hepatobiliary: (%) | Urinary tract: n | Urinary tract: (%) | Respiratory tract: n | Respiratory tract: (%) | Other: n [note 3] | Other: (%) [note 3] | Unknown: n [note 3] | Unknown: (%) [note 3] |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2012 to 2013 | 32,309 | 27,610 | 85.5 | 1,782 | 6.5 | 3,756 | 13.6 | 13,501 | 48.9 | 1,050 | 3.8 | 1,936 | 7.0 | 5,585 | 20.2 |
| 2013 to 2014 | 34,286 | 28,300 | 82.5 | 1,711 | 6 | 3,855 | 13.6 | 13,393 | 47.3 | 1,016 | 3.6 | 1,873 | 6.6 | 6,452 | 22.8 |
| 2014 to 2015 | 35,822 | 28,729 | 80.2 | 1,640 | 5.7 | 3,818 | 13.3 | 13,088 | 45.6 | 1,099 | 3.8 | 1,851 | 6.4 | 7,233 | 25.2 |
| 2015 to 2016 | 38,313 | 26,446 | 69.0 | 1,492 | 5.6 | 3,556 | 13.4 | 12,220 | 46.2 | 1,068 | 4.0 | 1,703 | 6.4 | 6,407 | 24.2 |
| 2016 to 2017 | 40,682 | 22,727 | 55.9 | 1,237 | 5.4 | 3,277 | 14.4 | 10,724 | 47.2 | 1,028 | 4.5 | 1,553 | 6.8 | 4,908 | 21.6 |
| 2017 to 2018 | 41,140 | 25,615 | 62.3 | 1,717 | 6.7 | 4,035 | 15.8 | 12,566 | 49.1 | 1,575 | 6.1 | 1,757 | 6.9 | 3,965 | 15.5 |
| 2018 to 2019 | 43,284 | 28,468 | 65.8 | 1,969 | 6.9 | 4,686 | 16.5 | 13,914 | 48.9 | 1,728 | 6.1 | 1,989 | 7.0 | 4,182 | 14.7 |
| 2019 to 2020 | 43,400 | 27,513 | 63.4 | 1,774 | 6.4 | 4,351 | 15.8 | 13,241 | 48.1 | 1,673 | 6.1 | 1,898 | 6.9 | 4,576 | 16.6 |
| 2020 to 2021 | 36,804 | 20,386 | 55.4 | 1,351 | 6.6 | 3,720 | 18.2 | 8,968 | 44.0 | 1,250 | 6.1 | 1,523 | 7.5 | 3,574 | 17.5 |
| 2021 to 2022 | 38,037 | 18,631 | 49.0 | 1,328 | 7.1 | 3,105 | 16.7 | 8,393 | 45.0 | 1,091 | 5.9 | 1,489 | 8.0 | 3,225 | 17.3 |
| 2022 to 2023 | 38,758 | 18,444 | 47.6 | 1,267 | 6.9 | 2,857 | 15.5 | 8,316 | 45.1 | 1,053 | 5.7 | 1,597 | 8.7 | 3,354 | 18.2 |
| 2023 to 2024 | 42,224 | 21,788 | 51.6 | 1,390 | 6.4 | 3,363 | 15.4 | 9,810 | 45.0 | 1,270 | 5.8 | 1,883 | 8.6 | 4,072 | 18.7 |
Note 1: financial year from April to March of the following year.
Note 2: gastrointestinal (not hepatobiliary).
Note 3: ‘Other’ includes the following options inputted on the HCAI DCS: bone and joint, central nervous system, genital tract (including prostate), indwelling intravascular device, other, respiratory tract, skin or soft tissue, no clinical signs of bacteraemia.
Note 4: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
In FY 2023 to 2024, the primary focus of E. coli bacteraemia also varied according to time-to-onset (duration between hospital admission and date of a positive specimen) (Table 3). Urinary tract as the primary focus was the most reported among time to-onset-groups. Furthermore, urinary tract as a primary focus was more common in cases where the time-to-onset was less than 2 days (47.1%) versus 2 and 6 days (30.4%) and 7 days or greater (37.2%).
Table 3. Distribution of primary focus E. coli bacteraemia, by time-to-onset, England: by financial year April 2023 to March 2024
| Time to onset (days) [note 1] | Gastrointestinal (not hepatobiliary) (number) | Gastrointestinal (not hepatobiliary) (%) [note 2] | Hepatobiliary (number) | Hepatobiliary (%) [note 2] | Urinary tract (number) | Urinary tract (%) [note 2] | Respiratory tract (number) | Respiratory tract (%) [note 2] | Other (number) | Other (%) [note 2] |
|---|---|---|---|---|---|---|---|---|---|---|
| Less than 2 | 457 | 5.0 | 1,457 | 15.9 | 4,321 | 47.1 | 416 | 4.5 | 638 | 7.0 |
| 2 to 6 | 185 | 12.5 | 295 | 20.0 | 448 | 30.4 | 86 | 5.8 | 195 | 13.2 |
| 7 and over | 346 | 11.4 | 345 | 11.4 | 1,128 | 37.2 | 208 | 6.9 | 465 | 15.3 |
Note 1: number of days from primary focus of infection to positive bacteraemia sample.
Note 2: proportion of cases by primary focus.
Geographic distribution of E. coli bacteraemia
The regional distribution of cases is presented across integrated care boards (ICBs) for FY 2023 to 2024, of which there was some geographical variation in rates of E. coli bacteraemia (Figure 8). There was clustering of high incidence rates in the Northern regions, South West and the Midlands. Accordingly, the highest rates (cases per 100,000 population) were found among ICBs within these areas; North East and North Cumbria ICB (94.2), Nottingham and Nottinghamshire ICB (93.0 cases per 100,000 population) and the Shropshire, Telford and Wrekin ICB (91.9). The lowest incidence rates were observed in Gloucestershire ICB (38.4), Bedfordshire, Luton and Milton Keynes ICB (51.6) and Leicester, Leicestershire and Rutland ICB (54.5).
Figure 8. Geographic distribution of E. coli bacteraemia rate, by integrated care boards, per 100,000 population, by financial year: April 2023 to March 2024
Note: Mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Mortality
In FY 2023 to 2024, 42,224 E. coli bacteraemia cases were reported in England. Information on mortality was available for 98.7% (41,656) of these cases. There were 6,040 deaths within 30 days of an E. coli bacteraemia diagnosis, a mortality rate of 10.6 deaths per 100,000 population and a case fatality rate (CFR) of 14.5%.
Similar to previous reports, there was a declining trend in CFR from the beginning of surveillance (FY 2012 to 2013, CFR: 16.8%), until FY 2018 to 2019 (CFR: 13.8%), after which the CFR increased to 16.1% by FY 2020 to 2021. In the last 3 years the trend in CFR has fluctuated with a CFR of 14.5% for FY 2023 to 2024. The mortality rate decreased slightly between FY 2022 to 2023 and FY 2023 to 2024 from 10.7 to 10.6 deaths per 100,000 population.
Figure 9. Case fatality rate and mortality rate of E. coli bacteraemia, England, by financial year: April 2012 to March 2024
Note: Mid-year population estimates for 2023 and 2024 were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Variation by onset of bacteraemia
In the last 3 years of surveillance, between FY 2021 to 2024, the CO mortality rate has increased from 7.2 to 7.5 deaths per 100,000 population. However, hospital-onset (HO) rates have fluctuated at around 4.8 cases per 100,000 population during the same period.
The CFR of HO cases declined from 22.6% to 21.6% between FY 2021 to 2022 and FY 2023 to 2024. CO cases also saw a decrease in CFR from 13.3% to 12.8% over the same period.
Variation by age and sex
In FY 2023 to 2024, among male cases, the highest mortality rates were observed in those aged 85 years and over (192.3 deaths per 100,000 population) and aged 75 to 84 years (67.6 deaths per 100,000 population). This equated to CFRs of 22.6% and 17.1%, respectively, indicating a slight decrease from the previous FY 2022 to 2023 which recorded CFRs of 24.6% and 18.6% for the same age groups. The mortality rate for both groups decreased by 3.1 and increased by 2.3 deaths per 100,000 population, from the previous year, respectively.
Similar to males, the highest mortality rates in females in FY 2023 to 2024 was seen in those aged over 85 years at 108.0 deaths per 100,000 population, followed by those aged 75 to 84 years at 39.4. This equated to CFRs of 19.1% and 13.5% of cases, respectively. Mortality rates and CFRs decreased in females aged 15 to 74 years.
Numbers of deaths are small in these groups so differences should be interpreted with caution.
Variation by region
Case fatality rates in FY 2023 to 2024 were highest in the Midlands region (15.3%) followed by East of England (15.2%) and North East and Yorkshire (15.1%). The CFR remained lowest in London (12.7%), the South East (13.8%) and South West of England (14.1%).
Epidemiological analysis of Gram-negative organisms: Klebsiella spp. bacteraemia
Total reports
A total of 13,078 cases of Klebsiella spp. bacteraemia were reported by NHS acute trusts in England in FY 2023 to 2024, an increase of 10.6% from FY 2022 to 2023 (n=11,828), marking the largest annual rise since the beginning of Klebsiella spp. surveillance in April 2017. Of these, 3,977 (30.4%) were hospital-onset cases (Figure 10). The total count of Klebsiella spp. BSI has increased year-on-year since the start of surveillance (FY 2017 to 2018) from 9,806 to 13,078. This increase was also reflected in the incidence rate of total Klebsiella spp. BSI cases, which increased from 17.6 cases per 100,000 population in FY 2017 to 2018 to 22.9 in FY 2023 to 2024.
Figure 10. Trends in the rate of Klebsiella spp. bacteraemia, England, by financial year: April 2017 to March 2024
Note: Mid-year population estimates for January to December 2023 onwards was unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Hospital and community-onset cases
Community-onset case rates (CO) have increased from 12.3 cases per 100,000 population to 13.9 between FY 2017 to 2018 and FY 2019 to 2020. Following this increase, CO rates declined (FY 2020 to 2021) reaching 13.1 and have since increased, we note a much rapid increase in the community-onset counts and rates from FY 2022 to 2023 from 7,893 to 9,101 and 13.8 to 15.9 in FY 2023 to 2024, marking the largest rise since the beginning of the surveillance in 2017 to 2018.
In contrast, the rate (cases per 100,000 overnight bed-days) of hospital-onset (HO) Klebsiella spp. cases was 8.4 in FY 2017 to 2018 increasing to 13.7 by FY 2020 to 2021. This observed increase has 2 components. Firstly, the number of hospital-onset cases increased from 3,225 to 3,795 between April 2019 and March 2021. Secondly, there was a drop off in hospital activity (occupied bed-days) between the April 2019 and March 2021 period which increased rates.
Hospital activity has since increased, contributing to the decrease in HO rate to 11.3 in the following year (FY 2021 to 2022), and 11.0 in FY 2023 to 2024.
Table 4. Klebsiella spp. bacteraemia counts and rates, England, by financial year: April 2017 to March 2024
| Financial year [note 1] | Mid-year population estimate [note 2] | All reported cases | Rate (all reported cases per 100,000 population) | Total bed-days | Hospital-onset cases | Rate (Hospital-onset cases per 100,000 bed-days) | Community-onset cases | Rate (Community-onset cases per 100,000 population) |
|---|---|---|---|---|---|---|---|---|
| 2017 to 2018 | 55,707,642 | 9,806 | 17.6 | 34,903,075 | 2,928 | 8.4 | 6,878 | 12.3 |
| 2018 to 2019 | 56,053,563 | 10,724 | 19.1 | 34,538,184 | 3,212 | 9.3 | 7,512 | 13.4 |
| 2019 to 2020 | 56,468,265 | 11,074 | 19.6 | 34,637,156 | 3,225 | 9.3 | 7,849 | 13.9 |
| 2020 to 2021 | 56,434,900 | 11,180 | 19.8 | 27,628,155 | 3,795 | 13.7 | 7,385 | 13.1 |
| 2021 to 2022 | 56,690,879 | 11,438 | 20.2 | 32,905,086 | 3,704 | 11.3 | 7,734 | 13.6 |
| 2022 to 2023 | 57,106,398 | 11,828 | 20.7 | 35,490,766 | 3,935 | 11.1 | 7,893 | 13.8 |
| 2023 to 2024 | 57,223,954 | 13,078 | 22.9 | 35,991,392 | 3,977 | 11.0 | 9,101 | 15.9 |
Note 1: financial year from April to March of the following year.
Note 2: mid-year population estimates for 2023 and 2024 were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Figure 11. Monthly counts of Klebsiella spp. bacteraemia by onset of infection, England, by financial year: April 2017 to March 2024
Distribution of Klebsiella species
In FY 2023 to 2024, Klebsiella pneumoniae (73.6%) was the most frequently reported species, followed by Klebsiella oxytoca (15.9%). This distribution was similar regardless of onset of infection (Table 5). Compared with 2022 to 2023, the biggest rise in Klebsiella species was seen in Klebsiella pneumoniae (12.0%).
Table 5. Counts and percentages of Klebsiella species bacteraemia, England, by financial year: April 2023 to March 2024
| Species | All cases | Proportion of all cases | Hospital-onset cases | Proportion of all cases (hospital-onset) | Community-onset cases | Proportion of all cases (community-onset) |
|---|---|---|---|---|---|---|
| K. pneumoniae | 9,630 | 73.6% | 2,892 | 22.1% | 6,738 | 51.5% |
| K. oxytoca | 2,080 | 15.9% | 615 | 4.7% | 1,465 | 11.2% |
| K. aerogenes | 502 | 3.8% | 213 | 1.6% | 289 | 2.2% |
| Other named species | 455 | 3.5% | 127 | 1.0% | 328 | 2.5% |
| Not speciated | 411 | 3.1% | 130 | 1.0% | 281 | 2.1% |
Prior trust exposure
In comparison to FY 2019 to 2020, FY 2023 to 2024 observed an increase in both the count and rate of HOHA Klebsiella spp. cases from 3,225 to 3,977. There was a corresponding increase in the rate of HOHA incidence from 9.3 cases per 100,000 bed-days to 11.0 (see Table S8 in the accompanying data spreadsheet).
COHA Klebsiella spp. cases have remained broadly similar since FY 2019 to 2020; an increase was observed in FY 2023 to 2024 with counts reaching 1,915, a 16.7% increase from the previous financial year (FY 2022 to 2023). The rate of COHA cases also increased by 14.3% from 4.2 to 4.8 cases per 100,000 overnight bed-days and day-admissions since FY 2023 to 2024.
Between FY 2019 to 2020 and FY 2023 to 2024, the number of cases and rate of COCA Klebsiella spp. BSI incidence increased, respectively, by 40.4% (from 5,093 to 7,150) and by 38.9% (from 9.0 to 12.5 cases per 100,000 population). This increase is more notable between FY 2022 to 2023 and FY 2023 to 2024, when the count and rate increase by 14.9% and 14.7% from 6,224 to 7,150 and 10.9 to 12.5, respectively. These comparisons should be interpreted with caution as FY 2019 to 2020 had 1,009 cases with no information, compared with one case in FY 2020 to 2021 and FY 2022 to 2023 and none for FY 2023 to 2024.
Figure 12. Proportion of prior trust exposure cases, by financial year, April 2019 to March 2024 in England
Age and sex distribution
For all age and sex analyses, cases in which the age and/or sex was missing or recorded as unknown were excluded. In FY 2017 to 2018, 8 cases were reported with ‘unknown’ age or sex versus 10 cases of ‘unknown’ age or sex in FY 2023 to 2024.
Figure 13 compares the age and sex distribution of Klebsiella spp. bacteraemia cases as a percentage of all reported cases in FY 2017 to 2018 and FY 2023 to 2024. There has been little change to the distribution of cases with most of the burden of infection being among males. In FY 2023 to 2024, the case burden remained highest in males aged 45 years and over, predominantly in men aged 75 to 84 years (19.0% of cases). A similar trend was seen in older females aged 45 to 64 years (8.8% of cases) and aged 75 to 84 years (8.8% of cases), but to a much lesser extent. This is consistent with what has been observed in FY 2017 to 2018.
Figure 13. Age and sex distribution of Klebsiella spp. bacteraemia by percentage of cases, England, by financial years: April 2017 to March 2018 and April 2023 to March 2024
Note: Mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
In FY 2023 to 2024, the incidence rates of Klebsiella spp. bacteraemia were greater in males than females, particularly among older age groups aged 45 years and over. The incidence rate increased in all age groups, for both sexes, between FY 2017 to 2018 and FY 2023 to 2024. In FY 2023 to 2024, both males and females had their highest rates among individuals aged 85 years and over at 278.8 and 95.8 per 100,000 population, respectively.
Trends in the age- and sex-specific rates of Klebsiella spp. bacteraemia are shown in Figure 14. Rates of Klebsiella spp. bacteraemia have increased across most age and sex groups between the start of the surveillance until FY 2019 to 2020; these increases were notable in males aged over 75 years, and to a lesser extent females aged over 75 years. Sharp declines were observed in these older age groups, in FY 2020 to 2021, which began to recover in the following financial year. In FY 2023 to 2024, we note a sharper increase in these older male and female age groups to the previous financial year, by 13.8%, from 128.2 to 145.9 cases per 100,000 population in males aged 75 to 84 years, and by 10.9%, from 251.3 to 278.8 cases per 100,000 population in the 85 years and older group. For females aged 85 years and over, the rates increased by 25.7%, from 76.2 to 95.8 cases per 100,000 population, while in those aged 75 to 84 years, the incidence rate increased by 11.2%, from 50.8 to 56.6 cases per 100,000 population.
The incidence rate in those aged under 1 year declined by 6.9% for females since FY 2022 to 2023. Since last year, both sexes also observed a decline in rate in those aged 1 to 14 years by 20.8% (2.4 to 1.9) in males and 12.5% (1.6 to 1.4) in females. However, we note a sharper rise in males aged under 1 year from FY 2022 to 2023 to FY 2023 to 2024, by 9.5% from 47.5 to 52.0. This group have been seeing annual increases since FY 2019 to 2020, not reflected in their female counterpart.
It should be noted, the numbers remain low across all years, and the rate and number of cases remain lower in this group compared to some of the previous years and thus should be interpreted with caution.
Figure 14. Trends in age group and sex rates of Klebsiella spp. bacteraemia, England, by financial year: April 2017 to March 2024
Note: Mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2023 was used as a proxy.
Trends by ethnicity
In FY 2023 to 2024, the observed incidence rate of Klebsiella spp. bacteraemia was highest in the White and Black ethnic groups (23.2 and 21.8 cases per 100,000 population, respectively), intermediate in the Asian ethnic group (17.0 cases per 100,000 population), and lowest in the Mixed and Other ethnic groups (7.8 and 5.6 cases per 100,000 population, respectively).
However, age-standardised incidence rates were substantially higher in those of Black ethnicity (38.8), followed by Asian (34.1), whereas incidence rate in the White ethnic group were amongst the lowest (21.6 cases per 100,000 population, respectively). Since April 2021, there were sharper rises in Black, Asian and Mixed ethnic groups, with the Mixed ethnic group seeing a much sharper rise from FY 2022 to 2023 to FY 2023 to 2024.
Figure 15 and supplementary Table 12 show the incidence of Klebsiella spp. bacteraemia by ethnicity between April 2018 and March 2024.
Figure 15. Klebsiella spp. Bacteraemia rate by ethnicity, England, by financial year: April 2018 to March 2024
Note 1: shaded bands indicate 95% confidence intervals.
Note 2: mid-year population estimates for January to December 2021 onwards were unavailable at time of publication and so population data for January to December 2020 was used as a proxy.
In FY 2023 to 2024, all ethnic groups, apart from Other, experienced the highest age-standardised rates of Klebsiella spp. bacteraemia since April 2018.
Trends by deprivation
In FY 2023 to 2024, 26.6 cases occurred per 100,000 people living in the 20% most deprived areas versus 19.5 cases per 100,000 people living in the 20% least deprived areas. The observed incidence rate of Klebsiella spp. bacteraemia increased with deprivation.
The difference in age-standardised incidence of Klebsiella spp. bacteraemia was greater or less to crude rates (34.9 and 16.5 cases per 100,000 population in the 20% most or 20% least deprived areas, respectively), over twice the difference in incidence rate. There was a sharper rise in incidence rate across IMD groups from FY 2022 to 2023 to FY 2023 to 2024, with the exception of the least 20% deprived areas, where the increase was more moderate.
Figure 16 and supplementary Table 13 in the accompanying spreadsheet show the incidence of Klebsiella spp. bacteraemia by deprivation between April 2018 and March 2024.
Figure 16. Klebsiella spp. Bacteraemia rate by deprivation, England, by financial year: April 2018 to March 2024
Note 1: shaded bands indicate 95% confidence intervals.
Note 2: mid-year population estimates for January to December 2021 onwards were unavailable at time of publication and so population data for January to December 2020 was used as a proxy.
There has been a consistent ordering of age-standardised Klebsiella spp. bacteraemia time series by increasing deprivation since April 2018.
Seasonal trends in Klebsiella spp. bacteraemia
In the first 3 financial years of Klebsiella spp. bacteraemia mandatory surveillance (between April 2017 to March 2020), the percentage of hospital-onset cases was greatest in the July to September quarters in this time period (see Table S7 in the accompanying data spreadsheet). FY 2020 to 2021 saw a considerable change in the percentage distribution by quarter for hospital-onset Klebsiella spp. cases. For the first time the percentage of cases increased in the October to December 2020 financial quarter with a further increase during January and March 2021. This is the first time since the start of Klebsiella spp. mandatory surveillance (FY 2017 to 2018) that this trend has been observed.
In FY 2023 to 2024, the percentage of hospital-onset cases increased during the July to September quarter and continued to rise in the October to December quarter before decreasing in the last financial quarter.
Between FY 2017 to 2018 and FY 2020 to 2021 the percentage of community-onset cases was greatest in the July to September quarter. In FY 2023 to 2024, this trend remained consistent.
Primary focus of Klebsiella spp. bacteraemia
Reporting of primary focus for Klebsiella spp. bacteraemia remains low; in FY 2023 to 2024 the primary focus was reported for 46.2% of all cases. The most frequently reported primary focus of Klebsiella spp. bacteraemia was the urinary tract, constituting 34.6% of cases with a reported primary focus of infection in FY 2023 to 2024. This percentage has remained broadly consistent since the inception of Klebsiella spp. surveillance (Table 6 and Table 7). Hepatobiliary and respiratory tract as primary foci have decreased between FY 2017 to 2018 and FY 2023 to 2024, from 20.2% to 16.6% and from 9.2% to 8.8%, respectively.
Table 6. Klebsiella spp. bacteraemia counts and rates by primary focus of bacteraemia, England, by financial year: April 2017 to March 2024
| Financial year | Total Klebsiella reported | Primary focus ascertained: n | Primary focus ascertained: (%) | Gastro-intestinal: n [note 1] | Gastro-intestinal: (%) [note 1] | Hepatobiliary: n | Hepatobiliary: (%) [note 2] | Urinary tract: n | Urinary tract: (%) | Respiratory tract: n | Respiratory tract: (%) | Other: n [note 3] | Other: (%) [note 3] | Unknown: n [note 3] | Unknown: (%) [note 3] | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2017 to 2018 | 9,806 | 5,110 | 52.1 | 374 | 7.3 | 1,032 | 20.2 | 1,681 | 32.9 | 470 | 9.2 | 603 | 11.8 | 950 | 18.6 | |
| 2018 to 2019 | 10,724 | 5,816 | 54.2 | 493 | 8.5 | 1,105 | 19.0 | 1,943 | 33.4 | 585 | 10.1 | 768 | 13.2 | 922 | 15.9 | |
| 2019 to 2020 | 11,074 | 6,108 | 55.2 | 484 | 7.9 | 1,221 | 20.0 | 2,056 | 33.7 | 581 | 9.5 | 745 | 12.2 | 1,021 | 16.7 | |
| 2020 to 2021 | 11,180 | 5,491 | 49.1 | 409 | 7.4 | 984 | 17.9 | 1,724 | 31.4 | 709 | 12.9 | 693 | 12.6 | 972 | 17.7 | |
| 2021 to 2022 | 11,438 | 5,255 | 45.9 | 367 | 7.0 | 938 | 17.8 | 1,729 | 32.9 | 550 | 10.5 | 745 | 14.2 | 926 | 17.6 | |
| 2022 to 2023 | 11,828 | 5,292 | 44.7 | 430 | 8.1 | 871 | 16.5 | 1,805 | 34.1 | 466 | 8.8 | 753 | 14.2 | 967 | 18.3 | |
| 2023 to 2024 | 13,078 | 6,042 | 46.2 | 432 | 7.1 | 1,003 | 16.6 | 2,093 | 34.6 | 532 | 8.8 | 788 | 13.0 | 1,194 | 19.8 |
Note 1: financial year from April to March of the following year.
Note 2: gastrointestinal (not hepatobiliary).
Note 3: ‘Other’ includes the following options inputted on the HCAI DCS: bone and joint, central nervous system, genital tract (including prostate), indwelling intravascular device, other, respiratory tract, skin or soft tissue, no clinical signs of bacteraemia.
Note 4: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
In FY 2023 to 2024, for inpatients with a time-to-onset of fewer than 2 days, the most common primary focus of bacteraemia was urinary tract (38.4%). As the time between admission and the onset of bacteraemia increases, the percentage of inpatients reporting the urinary tract as the primary focus decreases from 38.4% for those with onset in less than 2 days to 23.5% (for those with onset in 7 days or more).
Among those with a time-to-onset of less than 2 days, 6.0% had a respiratory focus and 4.6% had a gastrointestinal focus. These percentages increased to 12.5% and 12.7%, respectively, among individuals with a time-to-onset of 7 days or more. Caution is advised when interpreting these numbers due to low counts and annual fluctuations in trend.
Table 7. Distribution of primary focus of Klebsiella spp. bacteraemia cases, by time-to-onset, England: financial year April 2023 to March 2024
| Time to onset (days) [note 1] | Gastrointestinal (not hepatobiliary) (number) | Gastrointestinal (not hepatobiliary) (%) [note 2] | Hepatobiliary (number) | Hepatobiliary (%) [note 2] | Urinary tract (number) | Urinary tract (%) [note 2] | Respiratory tract (number) | Respiratory tract (%) [note 2] |
|---|---|---|---|---|---|---|---|---|
| Less than 2 | 103 | 4.6 | 411 | 18.2 | 868 | 38.4 | 136 | 6.0 |
| 2 to 6 | 62 | 11.5 | 103 | 19.1 | 117 | 21.7 | 55 | 10.2 |
| 7 or more | 174 | 12.7 | 146 | 10.7 | 321 | 23.5 | 171 | 12.5 |
Note 1: number of days from primary focus of infection to positive bacteraemia sample.
Note 2: proportion of cases by primary focus.
Geographic distribution of Klebsiella spp. bacteraemia
Regional distribution of cases is presented across ICBs for FY 2023 to 2024. There was more geographical variation in rates than has been observed for E. coli (Figure 17). The highest incidence rates were observed in the North East and North Cumbria ICB (29.3 cases per 100,000 population), Dorset ICB (26.9 cases per 100,000 population) and Humber and North Yorkshire ICB (26.9 cases per 100,000 population), while the lowest incidence rates were observed in Bedfordshire, Luton and Milton Keynes ICB (16.2 cases per 100,000 population), Herefordshire and Worcestershire ICB (16.6 cases per 100,000 population) and Gloucestershire ICB (17.1 cases per 100,000 population).
Figure 17. Geographic distribution of Klebsiella spp. bacteraemia rate, by integrated care boards, England, by financial year: April 2023 to March 2024
Note: mid-year population estimates for January to December 2023 were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Mortality
In FY 2023 to 2024, 13,078 Klebsiella spp. bacteraemia cases were reported in England. Information on mortality was available for 98.4% (12,863) of these cases. There were 2,461 deaths within 30 days of a Klebsiella spp. bacteraemia diagnosis, giving a mortality rate of 4.3 deaths per 100,000 population and a CFR of 19.1% (Figure 18).
Mandatory surveillance of Klebsiella spp. bacteraemia started in FY 2017 to 2018, as such, trends are not as established as some other collections. The mortality rate increased from 3.5 to 4.3 deaths per 100,000 population between FY 2017 to 2018 and FY 2023 to 2024. A steeper increase in mortality rate was also observed between FY 2022 to 2023 and FY 2023 to 2024, 7.5% from 4.0 to 4.3, coinciding with the steep increase in cases observed for the same period. Conversely, the CFR decreased marginally from 20.2% (1,928 deaths) to 19.1% (2,461 deaths) between FY 2017 to 2018 and FY 2023 to 2024.
Figure 18. Case fatality rate and mortality rate of Klebsiella spp. bacteraemia, England: financial year April 2017 to March 2024
Note: Mid-year population estimates for 2023 and 2024 were unavailable at time of publication and so population data for January to December 2023 was used as a proxy.
Variation by onset of bacteraemia
Between FY 2022 to 2023 and FY 2023 to 2024, the mortality rate of HO cases increased from 2.5 deaths per 100,000 bed-days (900 deaths) to 2.7 (961 deaths). Similarly, CFR for HO cases decreased from 23.4% to 24.7%.
The mortality rate in CO cases increased from 2.4 deaths per 100,000 population (1,372 deaths) in FY 2022 to 2023 to 2.6 (1,500 deaths) in FY 2023 to 2024. The corresponding CFRs decreased from 17.6% to 16.7%.
Variation by age and sex
In FY 2023 to 2024, the mortality rate and CFR increased with age, with the exception of those aged under 1 year. The mortality rate was greater in males while the CFR was greater in females.
For males, the highest mortality rate was observed in those aged over 85 years (70.9 deaths per 100,000 population) and those aged 75 to 84 years (29.7 deaths per 100,000 population) with corresponding CFRs of 25.6% and 20.5% of cases, respectively. Compared with FY 2022 to 2023, mortality rates for males aged over 85 years and aged 75 to 84 years increased by 4.1% and 12.9%, respectively.
For females, the highest mortality rate was also observed in those aged over 85 years (30.0 deaths per 100,000 population) and those aged 75 to 84 years (11.4 deaths per 100,000 population). CFRs for these groups were 31.3% and 20.5%, respectively. Compared to FY 2022 to 2023, mortality rates for females aged over 85 years increased by 24.0% and remained stable at 11.4 for those aged 75 to 84 years.
Variation by region
Case fatality rates in FY 2023 to 2024 were highest in the North West (20.2%) followed by East of England (20.1%) and North East and Yorkshire (19.4%). The CFR remained lowest in both London (17.6%) and the Midlands (18.9%).
Epidemiological analysis of Gram-negative organisms: Pseudomonas aeruginosa bacteraemia
Total reports
A total of 4,455 cases of P. aeruginosa bacteraemia were reported by NHS acute trusts in England in FY 2023 to 2024. Of the 4,455 P. aeruginosa cases, 1,714 (38.5%) were hospital-onset cases. There was little variation in the counts and rates of total P. aeruginosa cases since the start of enhanced surveillance in 2017, except for a spike in the rate of hospital-onset cases in FY 2020 to 2021 (Figure 19). Since, then the rate has declined and remains stable at 4.8 cases per 100,000 bed-days in FY 2023 to 2024.
Figure 19. Trends in the rate of P. aeruginosa bacteraemia, England, by financial year: April 2017 to March 2024
Note: Mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Hospital and community-onset cases
The rate (cases per 100,000 bed-days) of P. aeruginosa hospital-onset (HO) cases was relatively stable between FY 2017 to 2018 and FY 2019 to 2020, ranging from 4.6 to 4.7 cases per 100,000 overnight bed-days (Table 8); this increased to 6.0 in FY 2020 to 2021. This observed increase in rate was due to an increase in the reported number of hospital-onset cases, from 1,583 in FY 2019 to 2020 to 1,630 in FY 2021 to 2022, compounded by a decline in bed-days reported due to the COVID-19 pandemic; the hospital-onset rate reverted back in the following financial years, with a rate of 4.8 in FY 2023 to 2024.
Community-onset cases make up 61.5% of all reported P. aeruginosa cases. In comparison to HO rates, CO rates have remained stable averaging at 4.8 cases per 100,000 population over the 7 surveillance years.
Table 8. P. aeruginosa bacteraemia counts and rates, England, by financial year: April 2017 to March 2024
| Financial year [note 1] | Mid-year population estimate [note 2] | All reported cases | Rate (all reported cases per 100,000 population) | Total bed-days | Hospital-onset cases | Rate (Hospital-onset cases per 100,000 bed-days) | Community-onset cases | Rate (Community-onset cases per 100,000 population) |
|---|---|---|---|---|---|---|---|---|
| 2017 to 2018 | 55,707,642 | 4,309 | 7.7 | 34,903,075 | 1,626 | 4.7 | 2,683 | 4.8 |
| 2018 to 2019 | 56,053,563 | 4,191 | 7.5 | 34,538,184 | 1,521 | 4.4 | 2,670 | 4.8 |
| 2019 to 2020 | 56,468,265 | 4,348 | 7.7 | 34,637,156 | 1,583 | 4.6 | 2,765 | 4.9 |
| 2020 to 2021 | 56,434,900 | 4,291 | 7.6 | 27,628,155 | 1,670 | 6.0 | 2,621 | 4.6 |
| 2021 to 2022 | 56,690,879 | 4,342 | 7.7 | 32,905,086 | 1,630 | 5.0 | 2,712 | 4.8 |
| 2022 to 2023 | 57,106,398 | 4,410 | 7.7 | 35,490,766 | 1,699 | 4.8 | 2,711 | 4.7 |
| 2023 to 2024 | 57,223,954 | 4,455 | 7.8 | 35,991,392 | 1,714 | 4.8 | 2,741 | 4.8 |
Note 1: financial year from April to March of the following year.
Note 2: mid-year population estimates for 2023 and 2024 were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Figure 20. Monthly counts of P. aeruginosa bacteraemia by onset of infection, England, by financial year: April 2017 to March 2024
Prior trust exposure
In comparison to FY 2019 to 2020, an increase was observed to FY 2023 to 2024 in the number of HOHA P. aeruginosa cases, rising from 1,583 to 1,714 with a corresponding increase in the incidence rate of HOHA from 4.6 to 4.8 cases per 100,000 population – a 4.3% increase. Over the same period, the number of COHA cases increased by 10.6% from 727 to 813 cases, with the rate increasing from 1.9 to 2.0 cases per 100,000 overnight bed-days and day admissions in FY 2023 to 2024. COCA cases increased 21.1% from 1,583 to 1,917 and 17.9% from 2.8 to 3.3 cases per 100,000 population, respectively (see Table S8 in the accompanying data spreadsheet).
Figure 21. Proportion of prior trust exposure cases, by financial year, April 2019 to March 2024 in England
Age and sex distribution
Cases in which the age and or sex was missing or reported as ‘unknown’ were excluded. In both FY 2017 to 2018 and FY 2023 to 2024, 2 cases had an ‘unknown’ age or sex.
Figure 22 compares the age and sex distribution of P. aeruginosa cases as a percentage of all reported cases in FY 2017 to 2018 and FY 2023 to 2024. There has been little change to the distribution of cases. Most cases occurred in males and in adults aged 45 years and over. The highest proportion of cases for both sexes in FY 2023 to 2024 (20.5% of males and 8.0% of females) was among those aged 75 to 84 years. Similarly to Klebsiella spp., in FY 2023 to 2024, the percentage of male cases among those aged 15 to 44 years was similar to their female counterparts. This was not the case for E. coli bacteraemia.
Figure 22. Age and sex distribution of P. aeruginosa bacteraemia by percentage of cases, England, by financial years April 2017 to March 2018 and April 2023 to March 2024
Note: Mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
In FY 2023 to 2024, except for those aged under 1 year, the incidence rate of P. aeruginosa bacteraemia increased with age for both sexes; the highest rate observed for both sexes was among those aged 85 years and over. The rate in males aged 85 years and over between FY 2017 to 2018 to FY 2023 to 2024 has remained similar (Figure 22). Over the same period, the rate in females aged 85 years and over decreased 22.4% from 34.0 to 26.4 cases per 100,000 population.
Those aged under 1 year are a relatively high-risk group. Of note, between FY 2017 to 2018 and FY 2023 to 2024, the rate for both sexes in that age group increased. For females this increased by 77.3% from 6.6 to 11.7 and 36.5% from 9.6 to 13.1 in males, respectively. All other age groups remained comparable between the 2 financial years.
Trends in the age- and sex-specific rates of P. aeruginosa bacteraemia are shown in Figure 23. The rates are higher in males compared with females, especially in the older age groups (aged 65 years and over). Since FY 2017 to 2018, the incidence rate in males aged 85 and older has fluctuated between 89.0 and 109.4 cases per 100,000 population. In FY 2023 to 2024, there was a steep rise in the incidence rate for among males aged 85 years and over, 107.8, a 10.2% increase from the last financial year (FY 2022 to 2023). A similar rise is seen in males aged 75 to 84 years, of 14.0% from 47.0 to 53.6, for the same period. The rate of incidence for females aged over 85 years was 26.4 for FY 2023 to 2024, a 10.8% decrease since FY 2022 to 2023.
Generally, all other age groups, for both sexes, have remained broadly stable over the 7 years since the start of P. aeruginosa bacteraemia mandatory surveillance. The exception to this for both sexes was those aged under 1 year. Caution should be applied when interpreting this age group due to smaller case numbers.
Figure 23. Trends in age group and sex rates of P. aeruginosa bacteraemia cases, England, by financial year: April 2017 to March 2024
Note: Mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
In FY 2023 to 2024, the observed incidence rate of P. aeruginosa bacteraemia was highest in the Black and White ethnic groups (8.2 and 8.0 cases per 100,000 population, respectively). It was intermediate in the Asian ethnic group (4.6 cases per 100,000 population), and lowest in the Mixed and Other ethnic groups (2.6 and 2.2 cases per 100,000 population, respectively).
Age-standardised incidence rates are much greater than observed incidence in all except the White ethnic group. The Black ethnic group sees the highest incidence compared with Other ethnic groups consistently over the surveillance period and is steadily increasing. However, recent years have seen a plateau at 13.4 cases per 100,000 population. Asian and Other ethnic groups have fluctuated in the past 6 years without trend. The Mixed ethnic group has seen rises since April 2019, while the White ethnic group has remained relatively constant in FY 2023 to 2024 at 7.4 cases per 100,000 population.
Figure 24 and supplementary Table 12 in the accompanying data spreadsheet show the incidence of P. aeruginosa bacteraemia by ethnicity between April 2018 and March 2024.
Figure 24. P. aeruginosa bacteraemia rate by ethnicity, England, by financial year: April 2018 to March 2024
Note 1: shaded bands indicate 95% confidence intervals.
Note 2: mid-year population estimates for January to December 2021 onwards were unavailable at time of publication and so population data for January to December 2020 was used as a proxy.
Trends by deprivation
Unlike the other reported organisms, in FY 2023 to 2024, the observed incidence rate for P. aeruginosa bacteraemia did not substantially differ by deprivation, ranging between 7.5 to 8.8 cases per 100,000 population.
However, age-standardised incidence rates of P. aeruginosa bacteraemia varied more widely by deprivation with larger or smaller rates than observed, with 10.0 and 6.3 cases per 100,000 population in the 20% most or 20% least deprived areas, respectively.
Figure 25 and supplementary Table 13 in the accompanying data spreadsheet show the incidence of P. aeruginosa bacteraemia by deprivation between April 2018 and March 2024.
Figure 25. P. aeruginosa bacteraemia rate by deprivation, England, by financial year: April 2018 to March 2024
Note 1: shaded bands indicate 95% confidence intervals.
Note 2: mid-year population estimates for January to December 2021 onwards were unavailable at time of publication and so population data for January to December 2020 was used as a proxy.
Since April 2020 there has been an increasing trend in the second least deprived level, however other levels have fluctuated without trend.
Seasonal trends in P. aeruginosa bacteraemia
Seasonality was assessed as the number of cases each quarter as a percentage of total cases for the financial year. This analysis was performed separately for hospital-onset and community-onset cases. When assessing the distribution of community-onset P. aeruginosa cases per financial year, the greatest proportion of cases occur in the July to September quarter of each financial year. This has occurred for each year since the beginning of P. aeruginosa surveillance in FY 2017 to 2018. However, there has been no consistent trend in the distribution of hospital-onset cases by quarter for P. aeruginosa bacteraemia mandatory surveillance.
Primary focus of P. aeruginosa bacteraemia
Reporting of primary focus for P. aeruginosa remains low. In FY 2023 to 2024, the primary focus was reported for 45.1% of cases, a decrease from 49.4% from the start of surveillance in FY 2017 to 2018.
The most frequent primary focus of P. aeruginosa bacteraemia was the urinary tract, constituting 29.3% of cases in FY 2023 to 2024. Over the 7 financial years from April 2017 to March 2024, the percentage of primary focus reported as the urinary tract was similar (range: 28.7% to 31.1%) and was the most reported primary focus of bacteraemia (Table 9). As observed with Klebsiella spp., in the 3 financial years between April 2017 and March 2020 the percentage of cases reporting respiratory tract as a primary focus remained stable (range:13.0% to 14.1%). However, in FY 2020 to 2021, there was an increase in the percentage of primary focus reported as the respiratory tract to 16.1% which coincided with the first 2 waves of the COVID-19 pandemic. This reduced to 15.1% in FY 2021 to 2022 and then further declined to 12.4% by FY 2023 to 2024, in line with pre-pandemic levels.
Table 9. P. aeruginosa bacteraemia counts and rates by primary focus of bacteraemia, England, by financial year: April 2017 to March 2024
| Financial year | Total P.aeruginosa reported | Primary focus ascertained: n | Primary focus ascertained: (%) | Gastro-intestinal: n [note 1] | Gastro-intestinal: (%) [note 1] | Hepatobiliary: n | Hepatobiliary: (%) [note 2] | Urinary tract: n | Urinary tract: (%) | Respiratory tract: n | Respiratory tract: (%) | Other: n [note 3] | Other: (%) [note 3] | Unknown: n [note 3] | Unknown: (%) [note 3] | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2017 to 2018 | 4,309 | 2,129 | 49.4 | 126 | 5.9 | 102 | 4.8 | 638 | 30.0 | 300 | 14.1 | 491 | 23.1 | 472 | 22.2 | |
| 2018 to 2019 | 4,191 | 2,161 | 51.6 | 156 | 7.2 | 100 | 4.6 | 644 | 29.8 | 281 | 13.0 | 557 | 25.8 | 423 | 19.6 | |
| 2019 to 2020 | 4,348 | 2,320 | 53.4 | 160 | 6.9 | 123 | 5.3 | 716 | 30.9 | 313 | 13.5 | 549 | 23.7 | 459 | 19.8 | |
| 2020 to 2021 | 4,291 | 2,117 | 49.3 | 129 | 6.1 | 116 | 5.5 | 611 | 28.9 | 341 | 16.1 | 503 | 23.8 | 417 | 19.7 | |
| 2021 to 2022 | 4,342 | 1,931 | 44.5 | 117 | 6.1 | 93 | 4.8 | 600 | 31.1 | 291 | 15.1 | 461 | 23.9 | 369 | 19.1 | |
| 2022 to 2023 | 4,410 | 1,910 | 43.3 | 147 | 7.7 | 96 | 5.0 | 549 | 28.7 | 267 | 14.0 | 453 | 23.7 | 398 | 20.8 | |
| 2023 to 2024 | 4,455 | 2,011 | 45.1 | 147 | 7.3 | 108 | 5.4 | 589 | 29.3 | 250 | 12.4 | 501 | 24.9 | 416 | 20.7 |
Note 1: financial year from April to March of the following year.
Note 2: gastrointestinal (not hepatobiliary).
Note 3: ‘Other’ includes the following options inputted on the HCAI DCS: bone and joint, central nervous system, genital tract (including prostate), indwelling intravascular device, other, respiratory tract, skin or soft tissue, no clinical signs of bacteraemia.
Note 4: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
In FY 2023 to 2024, for inpatients with a time-to-onset (days between hospital admission and specimen date) of fewer than 2 days, the most important primary focus of bacteraemia was the urinary tract (31.3%). As time between admission and positive specimen increased, the percentage of inpatients reporting primary focus as the urinary tract decreased to 22.8% among those with a time-to-onset of 7 days or greater.
Conversely, as the number of days between admission and positive specimen increased, so did the percentage of individuals with a reported respiratory tract primary focus from 8.5% among those with fewer than 2 days, peaking at 16.8% in the 2 to 6 days group before declining to 11.9% among those with 7 days or greater. Similarly, gastrointestinal (not hepatobiliary) increased from 6.4% among those with less than 2 days to 7.9% in the 2 to 6 days group followed by an increase to 11.0% among those with 7 days or greater.
Table 10. Distribution of primary focus of P. aeruginosa bacteraemia cases, by time-to-onset, England, by financial year: April 2023 to March 2024
| Time to onset (days) [note 1] | Gastrointestinal (not hepatobiliary) (number) | Gastrointestinal (not hepatobiliary) (%) [note 2] | Hepatobiliary (number) | Hepatobiliary (%) [note 2] | Urinary tract (number) | Urinary tract (%) [note 2] | Respiratory tract (number) | Respiratory tract (%) [note 2] | Other (number) | Other (%) [note 2] |
|---|---|---|---|---|---|---|---|---|---|---|
| Less than 2 | 40 | 6.4 | 31 | 5.0 | 195 | 31.3 | 53 | 8.5 | 156 | 25.0 |
| 2 to 6 | 15 | 7.9 | 14 | 7.3 | 44 | 23.0 | 32 | 16.8 | 46 | 24.1 |
| 7 or more | 74 | 11.0 | 42 | 6.3 | 153 | 22.8 | 80 | 11.9 | 199 | 29.7 |
Note 1: number of days from primary focus of infection to positive bacteraemia sample.
Note 2: proportion of cases by primary focus.
Geographic distribution of P. aeruginosa bacteraemia
Regional distribution of cases is presented across ICB for FY 2023 to 2024. There was clustering of high incidence rates of P. aeruginosa in the Anglian regions while moderate rates are clustered across the country. Areas across the Midlands, North West and South West typically had lower rates (Figure 26). The highest incidence rate was observed in Buckinghamshire, Oxfordshire and Berkshire West ICB (10.3 cases per 100,000 population), Mid and South Essex ICB (9.8 cases per 100,000 population) and North Central London ICB (9.7 cases per 100,000 population), while the lowest incidence rates were observed in Gloucestershire ICB (3.8 cases per 100,000 population), Bedfordshire, Luton and Milton Keynes ICB (5.3 cases per 100,000 population) and West Yorkshire ICB (5.4 cases per 100,000 population).
Figure 26. Geographic distribution of P. aeruginosa bacteraemia rate, by Integrated Care Boards, England, by financial year: April 2023 to March 2024
Note: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Mortality
In FY 2023 to 2024, 4,455 P. aeruginosa bacteraemia cases were reported in England. Information on mortality was available for 98.2% (4,374) of these cases. There were 1,082 deaths within 30 days of a P. aeruginosa bacteraemia, with a mortality rate of 1.9 deaths per 100,000 population and a CFR of 24.7%.
Mandatory surveillance of P. aeruginosa bacteraemia started in FY 2017 to 2018, as such, trends are not as established as those in data collections such as MRSA or E. coli bacteraemia.
The CFR had decreased from 27.0% (1,144 deaths) in FY 2017 to 2018 to 24.7% (1,082 deaths) in FY 2023 to 2024. The mortality rate also remained consistent at around 1.9 deaths per 100,000 population between FY 2021 to 2022 and FY 2023 to 2024.
Figure 27. Case fatality rate and mortality rate of P. aeruginosa bacteraemia, England, by financial year: April 2017 to March 2024
Note: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Variation by onset of bacteraemia
Between FY 2019 to 2020 and FY 2023 to 2024, the CFR of HO cases increased slightly from 28.3% to 28.5%, while for CO cases over the same period the CFR had minor fluctuations but remained consistent around 22.4%. Compared with FY 2022 to 2023, CFR in HO cases in FY 2023 to 2024 decreased from 29.0% to 28.5%, with a similar decline in CO cases from 23.5% to 22.4%.
In FY 2023 to 2024, the mortality rate of HO cases declined slightly from 1.4 to 1.3 deaths per 100,000 bed-days (476 deaths) compared with 1.4 (482 deaths) in FY 2022 to 2023. Over the same period, the mortality rate in CO cases remained stable at 1.1 deaths per 100,000 population (630 deaths and 606 deaths, respectively).
Variation by age and sex
In FY 2023 to 2024, CFR and mortality rate increased with age, except among children aged under 1 year. The mortality rate was greater in males while the CFR was greater in females.
In FY 2023 to 2024, the highest mortality rates in males were in those aged 85 years and over (27.0 deaths per 100,000 population) and those aged 75 to 84 years (13.0 deaths per 100,000 population), which corresponded to CFRs of 25.3% and 24.7% of cases, respectively.
In female cases of the same age groups, the mortality rates were far lower than their male counterparts; 10.7 deaths per 100,000 population (aged 85 years and over) and 6.3 deaths per 100,000 population (aged 75 to 84 years). However, these equated to far higher CFRs than their male counterparts of 40.6% and 36.3% of all cases in these age groups.
Among children aged under one year, the mortality rate in males was 3.3 deaths per 100,000 population and 3.1 in females. As the number of deaths was relatively small in both sexes, caution is required in interpreting these data.
Variation by region
Case fatality rates in FY 2023 to 2024 were highest in the South East (27.4%) followed by North East and Yorkshire (26.4%) and North West (26.3%). The CFR remained lowest in London at 20.8% and East of England (23.6%).
E. coli, Klebsiella spp. and P. aeruginosa discussion and comparison
Data reported on E. coli, Klebsiella spp. and P. aeruginosa continues to show both similarities and differences in the epidemiological trends of these bacteraemia.
E. coli continues to have the highest count and rate of all the Gram-negative organisms, with 42,224 cases and a rate of 73.8 cases per 100,000 population reported in FY 2023 to 2024. This is followed by Klebsiella spp. (n = 13,078, 22.9) and then P. aeruginosa cases (n = 4,455, 7.8).
Long-term trends of each bacteraemia show increasing incidence rates since the start of enhanced surveillance until at least the start of the COVID-19 pandemic. E. coli cases, which were previously showing an ongoing annual increase, declined considerably during FY 2020 to 2021. Since then, the incidence rate has been increasing and has almost reached pre-pandemic levels in FY 2023 to 2024. Of particular concern is the recent increase observed between FY 2022 to 2023 and FY 2023 to 2024, marking the largest annual increase since the inception of E. coli surveillance. This is also true for Klebsiella spp., the increases are predominantly being driven by community-onset cases. Further work and thorough investigations are underway to investigate (some details available in the ‘Future work’ section of this report), however, more data is required to fully determine these changes in trend.
The observed decline of E. coli was not observed for Klebsiella spp. and P. aeruginosa bacteraemia. Further analysis conducted by the UK Health Security Agency (UKHSA) identified the increases corresponded with increases in hospital-onset cases that are a) secondary to COVID-19 cases, b) reported with respiratory tract as the primary focus of infection and c) reported in intensive care units (2). Suggesting that the increases in hospital-onset cases are likely related to the COVID-19 pandemic. E. coli bacteraemia is less commonly associated with these factors compared to Klebsiella spp. and P. aeruginosa potentially explaining the difference in trend. It is important to note the rate for Klebsiella spp. remained high compared to pre-pandemic levels, however, the rate for P. aeruginosa returned to similar levels in line with earlier years of surveillance.
Among the Gram-negative bacteraemia cases with a known primary focus of infection, the urinary tract remains a major source of bacteraemia for all Gram-negatives, accounting for 45.0% of E. coli, 34.6% of Klebsiella spp. and 29.3% of P. aeruginosa. In FY 2020 to 2021, P. aeruginosa and Klebsiella spp. had their highest percentage of infections reported with a respiratory tract as primary focus with 16.1% and 12.9%, respectively. This peak in the respiratory tract as focus of infection coincided with the months of highest counts and rates of SARS-CoV-2 infection during the second COVID-19 wave in England, with further investigations revealing a proportion as being co-infected with COVID-19 (2). This declined for both P. aeruginosa (12.4%) and Klebsiella spp. (8.8%) consecutively for the second financial year for FY 2023 to 2024, returning to reported pre-pandemic levels.
The age distribution of cases was similar in all 3 Gram-negative bacteraemias included in the mandatory surveillance programme. However, there were differences in the distribution of cases by sex. E. coli cases were more evenly distributed between male and female cases, while Klebsiella spp. and P. aeruginosa cases were more common in male cases, particularly in the older age groups.
Rates of each of the Gram-negative bacteraemia showed variations in geographic distributions in England with evidence of similar and relatively high infection rates among neighbouring ICBs for all 3 Gram-negative bacteraemia suggested by the observed data, although differences exist within the organism-specific patterns. More broadly, higher rates were generally found in each organism in the Northern and Midland regions of England.
Ethnicity and IMD data across all 3 Gram-negative bloodstream infections (GNBSIs) suggests those living in more deprived areas are disproportionately affected. Age-standardised ethnicity data also demonstrates ethnic minorities, particularly Black and Asian, having greater incidence of GNBSIs. It should be noted that ethnicity and deprivation are linked, with those in some ethnic minorities known to reside in more deprived areas. These findings highlight potential health inequalities, and a thorough investigation is planned to investigate potential drivers and inform appropriate interventions (see ‘Future works’ section).
The national action plan (NAP) published in 2019 was the first in a series of action plans intended to achieve the 20-year vision for AMR. To inform future policy the Department of Health and Social Care (DHSC) commissioned an evaluation of the first NAP, which marked a significant step forward in addressing AMR, both in the UK and globally. Building on these successes, the new national action plan, ‘Confronting Antimicrobial Resistance 2024 to 2029,’ aims to make further progress towards this 20-year vision of containing, controlling, and mitigating AMR. As part of the 2024 to 2029 NAP, there is a target on GNBSIs incidence: By 2029, there is an aim to prevent an increase in Gram-negative bloodstream infections in humans from the 2019 to 2020 financial year baseline.
Epidemiological analysis of Staphylococcus aureus bacteraemia
A total of 14,386 Staphylococcus aureus bacteraemia cases were reported in the financial year April 2023 to March 2024 (FY 2023 to 2024) through both the MRSA bacteraemia and MSSA bacteraemia surveillance schemes. This represents a 3.4% increase in the numbers of bacteraemia caused by S. aureus from the previous FY (2022 to 2023, n=13,912) and a 45.6% increase from the FY 2011 to 2012 (n=9,883) when MSSA reporting was made mandatory.
In FY 2023 to 2024, 6.3% (n=910) of S. aureus bacteraemia reports were caused by MRSA. This is a decrease from FY 2011 to 2012, in which 11.3% (n=1,116) of reports were caused by MRSA. This was also a small increase from the previous FY 2022 to 2023, in which only 5.7% (n=787) of reports were caused by MRSA. At its peak, FY 2007 to 2008, MRSA bacteraemia accounted for approximately 40% of all S. aureus bacteraemia cases in England.
The following sections describe the epidemiology of MRSA and MSSA in England separately.
Meticillin-resistant Staphylococcus aureus bacteraemia (MRSA)
Total reports
A total of 910 cases of MRSA bacteraemia were reported by NHS acute trusts in England in FY 2023 to 2024. This was a 15.6% increase since FY 2022 to 2023 (n=787), and a 79.6% decrease from FY 2007 to 2008 (n=4,451) when MRSA surveillance began. The rate of incidence has also declined from 8.6 cases per 100,000 population (FY 2007 to 2008) to 1.6 in FY 2023 to 2024. Figure 28 shows the trends in rates of MRSA cases for all cases and hospital-onset (HO) cases for FY 2007 to 2024, and community-onset (CO) cases since FY 2008 to 2009.
Figure 28. Trends in the all case and hospital-onset rate of MRSA bacteraemia, in England, by financial year: April 2007 to March 2024
Note: mid-year population estimates for 2023 and 2024 were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
The rate of all MRSA has plateaued since FY 2014 to 2015, ranging between 1.4 to 1.5 cases per 100,000 population. During this period of relative stability, a slight decline in rates was observed between FY 2019 to 2020 (1.4) and FY 2020 to 2022 (1.2) of 14.3%. Between FY 2022 to 2023 and FY 2023 to 2024, a shift in trend was observed, with MRSA cases increasing to 1.6 cases per 100,000 population, the highest incidence rate since FY 2013 to 2014.
Hospital and community-onset reports
Of the 910 cases reported in FY 2023 to 2024, 346 (38.0%) were hospital-onset (1.0 cases per 100,000 bed-days). Overall, there has been a declining trend in the rate of hospital-onset MRSA from 4.3 in FY 2008 to 2009 (when this metric was first collected) to 0.7 in FY 2021 to 2022 (Table 11). In FY 2023 to 2024, a 17.3% increase was observed in HO cases since FY 2022 to 2023 with a slight increase in rate from 0.8 to 1.0.
Since the inception of MRSA surveillance in FY 2008 to 2009, the percentage of cases that were hospital-onset declined from 54.7% to 38.0% in FY 2023 to 2024.
Similarly, community-onset rates (CO) have decreased from 2.6 to 1.0 case per 100,000 population between FY 2008 to 2009 and FY 2023 to 2024 with some marginal fluctuations during this period.
Table 11. MRSA counts and rates, England, by financial year: April 2007 to March 2024
| Financial year [note 1] | Mid-year population estimate [note 2] | All reported cases | Rate (all reported cases per 100,000 population) | Total bed-days | Hospital-onset cases | Rate (Hospital-onset cases per 100,000 bed-days) | Community-onset cases | Rate (Community-onset cases per 100,000 population) |
|---|---|---|---|---|---|---|---|---|
| 2007 to 2008 | 51,594,959 | 4,451 | 8.6 | 37,346,236 | - | - | - | - |
| 2008 to 2009 | 51,803,017 | 2,935 | 5.7 | 37,718,582 | 1,606 | 4.3 | 1,329 | 2.6 |
| 2009 to 2010 | 52,306,371 | 1,898 | 3.6 | 37,330,051 | 1,004 | 2.7 | 894 | 1.7 |
| 2010 to 2011 | 52,757,039 | 1,481 | 2.8 | 35,206,316 | 688 | 2.0 | 793 | 1.5 |
| 2011 to 2012 | 53,312,604 | 1,116 | 2.1 | 34,669,499 | 473 | 1.4 | 643 | 1.2 |
| 2012 to 2013 | 53,475,357 | 924 | 1.7 | 34,633,855 | 398 | 1.1 | 526 | 1.0 |
| 2013 to 2014 | 53,976,973 | 862 | 1.6 | 34,514,871 | 364 | 1.1 | 498 | 0.9 |
| 2014 to 2015 | 54,432,437 | 800 | 1.5 | 34,972,728 | 285 | 0.8 | 515 | 0.9 |
| 2015 to 2016 | 55,018,883 | 823 | 1.5 | 34,752,604 | 298 | 0.9 | 525 | 1.0 |
| 2016 to 2017 | 55,240,934 | 825 | 1.5 | 35,148,014 | 315 | 0.9 | 510 | 0.9 |
| 2017 to018 | 55,707,642 | 850 | 1.5 | 34,903,075 | 276 | 0.8 | 574 | 1.0 |
| 2018 to 2019 | 56,053,563 | 807 | 1.4 | 34,538,184 | 271 | 0.8 | 536 | 1.0 |
| 2019 to 2020 | 56,468,265 | 815 | 1.4 | 34,637,156 | 260 | 0.8 | 555 | 1.0 |
| 2020 to 2021 | 56,434,900 | 696 | 1.2 | 27,628,155 | 280 | 1.0 | 416 | 0.7 |
| 2021 to 2022 | 56,690,879 | 675 | 1.2 | 32,905,086 | 233 | 0.7 | 442 | 0.8 |
| 2022 to 2023 | 57,106,398 | 787 | 1.4 | 35,490,766 | 295 | 0.8 | 492 | 0.9 |
| 2023 to 2024 | 57,223,954 | 910 | 1.6 | 35,991,392 | 346 | 1.0 | 564 | 1.0 |
Note 1: financial year from April to March of the following year.
Note 2: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Figure 29. Monthly counts of MRSA bacteraemia by onset of infection, April 2007 to March 2024
Prior trust exposure
In FY 2023 to 2024, there was a 33.1% increase from 260 to 346 for HOHA cases compared to FY 2019 to 2020. A slight increase in rate from 0.8 to 1.0 cases per 100,000 bed-days was also observed. Conversely, for the same period, the number of reported COHA cases decreased by 9.8% (from 142 to 128), with a 25% decline in rate. FY 2019 to 2020 and FY 2023 to 2024.
COCA cases for FY 2023 to 2024 (n=433) have exceeded FY 2019 to 2020 (n=404) by 7.2%, for the first year since the start of prior trust exposure collection. With this increase, the COCA rate has also surpassed the FY 2019 to 2020 rate of 0.7 by 14.3% (0.8 in FY 2023 to 2024).
The underlying numbers are relatively small so caution should be exercised during interpretation.
Figure 30. Proportion of prior trust exposure cases, by financial year, April 2019 to March 2024 in England
Age and sex distribution
For all age and sex analyses, cases in which the age and/or sex was missing or recorded as unknown were excluded. In FY 2007 to 2008, 53 cases (1.2%) were reported with age or sex as unknown while in FY 2023 to 2024, no cases were reported with age or sex as unknown.
Figure 31 shows the age and sex distribution of MRSA cases as a percentage of all reported cases at the start of MRSA surveillance (FY 2007 to 2008) versus FY 2023 to 2024. The case burden is lower across most age groups in FY 2023 to 2024 versus FY 2007 to 2008, with the greatest reduction seen in older ages (65 years and over).
This is particularly evident for males and females aged 65 to 74 years. In FY 2023 to 2024, the proportion of cases in this age group reduced from 13.3% and 6.9% (FY 2007 to 2008), to 10.2% in males and 5.9% in females, respectively.
Conversely, the younger age groups have seen a relative increase, particularly in children aged 14 years and younger.
Figure 31. Age and sex distribution of MRSA bacteraemia by percentage of cases, England, by financial years: April 2007 to March 2008 and April 2023 to March 2024
At the start of MRSA surveillance (FY 2007 to 2008), higher MRSA rates were found in males in comparison to females, across all age groups. This remains true for FY 2023 to 2024, with the greatest difference in rates observed in males aged 85 years and over, with a rate of 17.0 rivalling that of 6.4 in females. Both sexes observed increasing rates of infection with age, with the exception among those aged under 1 year.
Caution is advisable when interpreting data for MRSA among those aged 14 years and under as the number of cases is small.
Since the start of MRSA surveillance, there have been huge reductions in the number of bacteraemia reported, this decrease is reflected in the age- and sex-specific rates and trends of MRSA bacteraemia (Figure 32).
When comparing FY 2007 to 2008 and FY 2023 to 2024, the sharpest decline for both sexes is observed in those aged 75 to 84 years, from 73.1 (89.6% decline) to 7.6 in males and from 26.3 to 2.8 (89.4% decline) in females. Those aged 85 years and over also observed similar sharp declines for both sexes from 147.4 to 17.0 (88.4% decline) and from 44.2 to 6.4 (85.5% decline), respectively. The decline in younger age groups has been relatively moderate, with increases noted for females in those aged 1 to 14 years, from 0.3 to 0.4 (33.3% increase). Males in the same group observed the same rate of 0.5 cases per 100,000 population.
Figure 32. Trends in age group and sex rates of MRSA bacteraemia cases, England, by financial year: April 2017 to March 2024
Note: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Trends by ethnicity
In FY 2023 to 2024, the observed incidence rate of MRSA bacteraemia varied rates were highest in the Black, Asian, and White ethnic groups (2.4, 1.9 and 1.5 cases per 100,000 population, respectively) and lowest in the Mixed and Other ethnic groups (1.1 and 0.6 cases per 100,000 population, respectively).
The highest age-standardised rate in FY 2023 to 2024 was observed in the Black ethnic group (3.7), followed by the Asian ethnic group (2.9 cases per 100,000 population, respectively). We also note a much sharper rise in the Black ethnic group from FY 2022 to 2023 to FY 2023 to 2024, overtaking the Asian ethnic group quite substantially compared with the previous year.
Figure 33 and supplementary Table 12 show the incidence of MRSA bacteraemia by ethnicity between April 2018 and March 2024.
Figure 33. MRSA bacteraemia rate by ethnicity, England, by financial year: April 2018 to March 2024
Note 1: shaded bands indicate 95% confidence intervals.
Note 2: mid-year population estimates for January to December 2021 onwards were unavailable at time of publication and so population data for January to December 2020 was used as a proxy.
Note 3: age-standardised rates for Mixed and Other ethnic groups could not be calculated when their yearly counts were less than 10 for any given ethnic-age subgroup. Therefore, the age-standardised rates for the Mixed ethnic group have high uncertainty in the last 2 financial years it could be calculated and should be treated with caution.
Trends by deprivation
In FY 2023 to 2024, 2.2 cases per 100,000 people occurred in those living in the 20% most deprived areas versus 1.2 cases per 100,000 people living in the 20% least deprived areas.
Age-standardised incidence rates show a much greater or lower incidence of MRSA bacteraemia than observed, with 2.6 and 1.0 cases per 100,000 population in the 20% most or 20% least deprived areas, respectively. Since April 2022 the 20% to 40% most deprived level has seen the greatest change in age-standardised incidence of MRSA bacteraemia, increasing more sharply compared with other areas.
Figure 34 and supplementary Table 13 show the incidence of MRSA bacteraemia by deprivation between April 2018 and March 2024.
Figure 34. MRSA bacteraemia rate by deprivation, England, by financial year: April 2018 to March 2024
Note 1: shaded bands indicate 95% confidence intervals.
Note 2: mid-year population estimates for January to December 2021 onwards were unavailable at time of publication and so population data for January to December 2020 was used as a proxy.
Source of MRSA bacteraemia
The Healthcare Associated Infections (HCAI) Data Capture System (DCS) provides NHS trust users the opportunity to add information regarding the likely source of bacteraemia. Source of bacteraemia refers to the likely cause of the bacteraemia, such as an intravenous catheter, rather than an organ where the infection first arose as in primary focus for Gram-negative bacteraemia. The provision of this information is voluntary and has declined over time for MRSA. In FY 2007 to 2008, a total of 54.2% (n=2,414) of MRSA records had entries (including ‘Unknown’) for the source of bacteraemia. By FY 2023 to 2024, only 25.5% (n=232) MRSA records had entries for the source of bacteraemia.
Among MRSA cases with a reported source of bacteraemia, there were large declines in the percentage of MRSA cases in which the source of bacteraemia was a catheter or line between FY 2007 to 2008 and FY 2014 to 2015 period from 25.6% to 11.9%. However, between FY 2014 to 2015 period and FY 2023 to 2024; this had increased to 17.7%. In contrast, the proportion of cases caused by skin and soft tissue infections there has seen continual increase from 16.4% in FY 2007 to 2008 to 36.6% in FY 2023 to 2024.
Between FY 2007 to 2008 and FY 2014 to 2015, the percentage of cases for which the source of bacteraemia was pneumonia increased from 6.6% to 15.4%. However, this then plateaued until FY 2020 to 2021 (range: 13.1% to 15.4%). The percentage attributed to pneumonia subsequently saw a sharp decline in FY 2021 to 2022 to 6.3%. However, for FY 2023 to 2024, the percentage of cases have seen an increase to 9.5%.
The underlying numbers are relatively small so caution should be exercised during interpretation. Trends in sources of bacteraemia are shown in Table 12.
Table 12. MRSA counts and rates by source of bacteraemia, England, by financial year: April 2007 to March 2023
| Financial year [note 1] | Total MRSA | Source of bacteraemia reported: n | Source of bacteraemia reported: (%) | Catheters and lines (number) [note 2] | Catheters and lines (%) [note 2] | Skin and soft tissue (number) | Skin and soft tissue (%) | Pneumonia (number) | Pneumonia (%) | Other (number) [note 3] | Other (%) [note 3] | Unknown (number) | Unknown (%) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2007 to 2008 | 4,451 | 2,414 | 54.2 | 617 | 25.6 | 395 | 16.4 | 160 | 6.6 | 705 | 29.2 | 537 | 22.2 |
| 2008 to 2009 | 2,935 | 1,541 | 52.5 | 346 | 22.5 | 276 | 17.9 | 113 | 7.3 | 552 | 35.8 | 254 | 16.5 |
| 2009 to 2010 | 1,898 | 915 | 48.2 | 178 | 19.5 | 191 | 20.9 | 63 | 6.9 | 328 | 35.8 | 155 | 16.9 |
| 2010 to 2011 | 1,481 | 676 | 45.6 | 118 | 17.5 | 146 | 21.6 | 47 | 7 | 251 | 37.1 | 114 | 16.9 |
| 2011 to 2012 | 1,116 | 482 | 43.2 | 71 | 14.7 | 98 | 20.3 | 41 | 8.5 | 177 | 36.7 | 95 | 19.7 |
| 2012 to 2013 | 924 | 394 | 42.6 | 72 | 18.3 | 74 | 18.8 | 34 | 8.6 | 128 | 32.5 | 86 | 21.8 |
| 2013 to 2014 | 862 | 294 | 34.1 | 39 | 13.3 | 57 | 19.4 | 33 | 11.2 | 100 | 34 | 65 | 22.1 |
| 2014 to 2015 | 800 | 253 | 31.6 | 30 | 11.9 | 53 | 20.9 | 39 | 15.4 | 64 | 25.3 | 67 | 26.5 |
| 2015 to 2016 | 823 | 245 | 29.8 | 38 | 15.5 | 56 | 22.9 | 25 | 10.2 | 89 | 36.3 | 37 | 15.1 |
| 2016 to 2017 | 825 | 255 | 30.9 | 51 | 20 | 80 | 31.4 | 21 | 8.2 | 88 | 34.5 | 15 | 5.9 |
| 2017 to 2018 | 850 | 325 | 38.2 | 50 | 15.4 | 101 | 31.1 | 40 | 12.3 | 118 | 36.3 | 16 | 4.9 |
| 2018 to 2019 | 807 | 289 | 35.8 | 37 | 12.8 | 97 | 33.6 | 30 | 10.4 | 115 | 39.8 | 10 | 3.5 |
| 2019 to 2020 | 815 | 258 | 31.7 | 33 | 12.8 | 81 | 31.4 | 24 | 9.3 | 96 | 37.2 | 24 | 9.3 |
| 2020 to 2021 | 696 | 214 | 30.8 | 34 | 15.9 | 55 | 25.7 | 28 | 13.1 | 91 | 42.5 | 6 | 2.8 |
| 2021 to 2022 | 675 | 176 | 26.1 | 31 | 17.6 | 60 | 34.1 | 11 | 6.3 | 65 | 36.9 | 9 | 5.1 |
| 2022 to 2023 | 787 | 224 | 28.5 | 37 | 16.5 | 82 | 36.6 | 16 | 7.1 | 79 | 35.3 | 10 | 4.5 |
| 2023 to 2024 | 910 | 232 | 25.5 | 41 | 17.7 | 85 | 36.6 | 22 | 9.5 | 78 | 33.6 | 6 | 2.6 |
Note 1: financial year from April to March.
Note 2: catheters and lines include the following options from the HCAI DCS question: dialysis lines, central venous catheter (CVC) associated, peripheral venous catheter (PVC) associated and intravenous (IV) lines.
Note 3: ‘Other’ includes the following options HCAI DCS: endocarditis, osteomyelitis, other, prosthetic joint, surgical site infection (SSI), septic arthritis, urinary tract and ventilator-associated pneumonia.
Geographic distribution of MRSA bacteraemia
Regional distribution of cases is presented across ICB for FY 2023 to 2024. While the overall rate of MRSA is comparatively low, there is some evidence of similar and relatively high incidence rates among some neighbouring ICBs (Figure 35). Broadly speaking the majority of ICBs have an average rate of less than 1.4 MRSA bacteraemia cases per 100,000 population. The highest incidence rates were observed in; Mid and South Essex ICB (3.5 cases per 100,000 population), Bristol, North Somerset and South Gloucestershire ICB (3.4 cases per 100,000 population) and South East London ICB (2.7 cases per 100,000 population), while the lowest incidence rate were observed in Gloucestershire ICB (0.5 cases per 100,000 population), Norfolk and Waveney ICB (0.6 cases per 100,000 population) and Nottingham and Nottinghamshire ICB (both 0.8 cases per 100,000 population).
Figure 35. Geographic distribution of MRSA rates, England, by financial year: April 2023 to March 2024
Note: mid-year population estimates for January to December 2023 were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Mortality
In FY 2023 to 2024, 910 MRSA bacteraemia cases were reported in England. Information on mortality was available for 98.6% (897 reports) of these cases. There were 208 deaths within 30 days of an MRSA bacteraemia diagnosis, a mortality rate of 0.4 deaths per 100,000 population. The CFR was 23.2% of cases.
The CFR has been declining since the start of the surveillance (FY 2007 to 2008) compared to FY 2023 to 2024, 23.2% versus 38.9%, respectively. The overall trend of mortality rate decreased from 2.6 to 0.4 deaths per 100,000 population.
Figure 36. Case fatality rate and all-cause mortality rate of MRSA bacteraemia, England, by financial year: April 2007 to March 2024
Note: mid-year population estimates for January to December 2023 were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Variation by onset of bacteraemia
The mortality rate of CO cases has remained consistent at 0.2 deaths per 100,000 population since FY 2018 to 2019 (Table S15 of the accompanying data spreadsheet). In comparison, the mortality rate of HO cases increased from 0.2 in FY 2022 to 2023, to 0.3 deaths per 100,000 bed-days (94 deaths) in FY 2023 to 2024.
In FY 2023 to 2024, the CFR decreased in HO cases from 29.6% to 27.7% and increased in CO cases from 18.2% to 20.4%, versus FY 2022 to 2023.
Variation by age and sex
In FY 2023 to 2024, except for those aged under 1 years, mortality rate and CFR increased with age. Over the same period, the mortality rate and CFR was greater in males.
The highest mortality rate in males was in those aged 85 years and over (8.3 deaths per 100,000 population) and those aged 75 to 84 years (2.4 deaths per 100,000 population), with CFRs being 48.9% and 31.0%, respectively.
In females, the mortality rate was also higher in the oldest age groups, 2.8 deaths per 100,000 population among those aged 85 years and over and 1.2 deaths per 100,000 population among those in the group aged 75 to 84 years. CFRs of these 2 groups were 44.6% and 42.1%, respectively.
Compared with other infections covered in this report, there were relatively fewer deaths in cases aged under one year compared with other age groups, however CFR in those aged under 1 year remained slightly elevated at 7.1% in females and 4.8% in males. In FY 2023 to 2024, there were 0 deaths within 30-days in males aged 1 to 14 years.
Variation by region
Case fatality rates in FY 2023 to 2024 were highest in the South West (29.3%) followed by Midlands (27.9%) and East of England (26.9%). The CFR remained lowest in London at 16.1% and North West (19.7%).
MRSA overview of trends and important analysis
MRSA bacteraemia rates declined consistently each year between FY 2007 to 2008 and FY 2014 to 2015. In FY 2015 to 2016, the rate increased slightly but remained relatively stable until FY 2020 to 2021, when there was a considerable decline in the rate of all reported cases compared to the previous years. Counts and rates for the past 2 years, however, have shifted to an increasing trend, with counts and rates for the first time reaching FY 2012 to 2013 levels. An increase in hospital-onset cases was observed between FY 2022 to 2023 and FY 2022 to 2023, with the rate increasing from 0.8 cases per 100,000 bed-days to 1.0.
Numerous interventions aimed at reducing the incidence of MRSA bacteraemia and other infections have been introduced from the beginning of the surveillance programme for MRSA, contributing to the large reductions seen. These include the Department of Health (DoH) policy document ‘Winning Ways,’ published in 2003, the ‘Clean Your Hands’ campaign launched by the National Patient Safety Agency in 2014, the ‘Saving Lives’ programme launched by the DoH in 2005 which included the ambition to halve MRSA rates by 2008, the 2006 Health Act which introduced a code of practice to provide guidance on reducing HCAI including MRSA, and the Health and Social Care Act, 2008 which requires the code of practice to be regularly updated.
The epidemiology of MRSA has changed since its peak in FY 2007 to 2008, and since FY 2010 to 2011 community-onset cases have been the most common. This switch in setting is most likely due to most MRSA bacteraemia interventions being concentrated in the acute care setting, and thus the largest reductions in MRSA bacteraemia’s were seen in hospital-onset cases. The duration of stay of hospital patients is also on the decline. In 2001 the average length of stay for a hospitalised patient was 7.4 days in the UK, this decreased to 6.2 days in 2019. The reduced hospital stay lessens the risk of acquiring a hospital-acquired infection (HAI).
The percentage of MRSA bacteraemia where the likely source of infection was a catheter or a line has shown steady decrease since the early years of surveillance, however between FY 2019 to 2020 and FY 2021 to 2022, the percentage increased from 12.8% to 17.6%. In FY 2023 to 2024, the percentage decreased to 17.2% in line with earlier years of surveillance. Despite some fluctuations in the recent years, an overall decline is observed from the start of the surveillance period.
The initial declines in the percentage of MRSA bacteraemia where the most likely source of infection is a catheter or line have been noted previously and may have been due to greater clinical awareness of the importance of this route of infection, the introduction of care bundles aimed at reducing infections in intravascular lines and selective decolonisation of patients with MRSA carriage. After the increase observed in the last financial year, the decline in the current year may be an indicator of recovery from the pandemic but will require further investigation to determine exact cause. Please note that the numbers that make up this period are relatively small compared to those observed at the MRSA peak.
The percentage where the source of bacteraemia is something other than catheters or intravenous lines have fluctuated considerably over time. The percentage of infections whose likely source is skin, or soft tissue infection does appear to have increased over time, from 16.4% in FY 2007 to 2008 to 36.6% in FY 2023 to 2024. However, during FY 2022 to 2023 only a quarter (29.2%) of records had information on the likely source of bacteraemia and therefore, interpretation of this data should be approached cautiously.
It is also noted that cases are more prevalent in the most deprived areas of England, and those of an ethnic minority background, mostly Black and Asian, highlighting potential health inequalities. There was also a very steep rise in the Black ethnic group in the most recent financial year.
The marginal increase in the rate of hospital-onset cases but decrease in the percentage of infections due to catheters and lines since FY 2014 to 2015 may point to a need to continue concentration on NHS trust-based infection prevention initiatives to reduce hospital-onset cases further. In addition to maintaining good practice in an acute trust setting, interventions are required in the community setting, considering most MRSA cases are community-onset.
Meticillin-susceptible Staphylococcus aureus bacteraemia (MSSA)
Total reports
A total of 13,476 cases of MSSA bacteraemia were reported by NHS acute Trusts in England in FY 2023 to 2024, an increase of 2.6% compared to FY 2022 to 2023 (n=13,129), and an increase of 53.7% versus FY 2011 to 2012 (n=8,767). Figure 37 shows the trends in rates of MSSA cases for all cases and hospital-onset cases between the start of MSSA mandatory surveillance (in FY 2011 to 2012) and FY 2023 to 2024.
The rate of all MSSA cases per 100,000 population, per year has risen from 16.4 during FY 2011 to 2012 to 23.5 in FY 2023 to 2024. When compared to pre-pandemic FY 2019 to 2020 (21.7) an 8.3% increase is observed.
Figure 37. Trends in the rate of MSSA bacteraemia in England, by financial year: April 2011 to March 2024
Note: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Hospital and community-onset reports
Between FY 2011 to 2012 and FY 2019 to 2020, the hospital-onset (HO) incidence rate has steadily increased from 8.2 cases to 9.6 per 100,000 overnight bed-days, an increase of 17.1%. In FY 2020 to 2021, the HO incidence rate increased sharply to 12.1 (n=3,341 of 11,705), a one-year increase of 26.0%. Of note, hospital activity was reduced compared with other years in FY 2020 to 2021. The HO rate subsequently declined in FY 2023 to 2024, to 10.8 cases per 100,000 overnight bed-days (n=3,881 of 13,476); although the rate has declined, it is still higher than pre-pandemic levels.
Community-onset cases (CO) has similarly increased year-on-year, from 11.1 cases per 100,000 population to 15.8 in FY 2019 to 2020. The rate then declined to 14.8 in FY 2020 to 2021, the only year recorded with a decline in trend. The rate has since increased to 16.8 in FY 2023 to 2024.
Table 13. MSSA counts and rates, England, by financial year: April 2011 to March 2024
| Financial year [note 1] | Mid-year population estimate [note 2] | All reported cases | Rate (all reported cases per 100,000 population) | Total bed-days | Hospital-onset cases | Rate (Hospital-onset cases per 100,000 bed-days) | Community-onset cases | Rate (Community-onset cases per 100,000 population) |
|---|---|---|---|---|---|---|---|---|
| 2011 to 2012 | 53,312,604 | 8,767 | 16.4 | 34,669,499 | 2,854 | 8.2 | 5,913 | 11.1 |
| 2012 to 2013 | 53,475,357 | 8,812 | 16.5 | 34,633,855 | 2,700 | 7.8 | 6,112 | 11.4 |
| 2013 to 2014 | 53,976,973 | 9,290 | 17.2 | 34,514,871 | 2,696 | 7.8 | 6,594 | 12.2 |
| 2014 to 2015 | 54,432,437 | 9,863 | 18.1 | 34,972,728 | 2,807 | 8.0 | 7,056 | 13.0 |
| 2015 to 2016 | 55,018,883 | 10,609 | 19.3 | 34,752,604 | 2,921 | 8.4 | 7,688 | 14.0 |
| 2016 to 2017 | 55,240,934 | 11,499 | 20.8 | 35,148,014 | 3,098 | 8.8 | 8,401 | 15.2 |
| 2017 to 2018 | 55,707,642 | 11,955 | 21.5 | 34,903,075 | 3,154 | 9.0 | 8,801 | 15.8 |
| 2018 to 2019 | 56,053,563 | 12,103 | 21.6 | 34,538,184 | 3,330 | 9.6 | 8,773 | 15.7 |
| 2019 to 2020 | 56,468,265 | 12,242 | 21.7 | 34,637,156 | 3,311 | 9.6 | 8,931 | 15.8 |
| 2020 to 2021 | 56,434,900 | 11,705 | 20.7 | 27,628,155 | 3,341 | 12.1 | 8,364 | 14.8 |
| 2021 to 2022 | 56,690,879 | 12,307 | 21.7 | 32,905,086 | 3,714 | 11.3 | 8,593 | 15.2 |
| 2022 to 2023 | 57,106,398 | 13,129 | 23.0 | 35,490,766 | 3,902 | 11.0 | 9,227 | 16.2 |
| 2023 to 2024 | 57,223,954 | 13,476 | 23.5 | 35,991,392 | 3,881 | 10.8 | 9,595 | 16.8 |
Note 1: financial year from April to March
Note 2: mid-year population estimates for 2023 and 2024 were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Figure 38. Monthly counts of MSSA bacteraemia by onset of infection, April 2011 to March 2024
Prior trust exposure
In comparison to FY 2022 to 2023, FY 2023 to 2024 observed a 0.5% decrease in the count of HOHA MSSA bacteraemia from 3,902 to 3,881, with a corresponding decrease in the rate of HOHA incidence from 11.0 to 10.8 cases per 100,000 bed-days.
COHA cases increased by 8.2% from 1,591 to 1,722, with the rate also increasing by 4.9% from 4.1 to 4.3 cases per 100,000 overnight bed-days and day admissions. Between the previous reporting financial year, COCA increased from 7,597 to 7,840 (3.2%) which corresponded to an increase in the COCA rate (3.0%) from 13.3 to 13.7 cases per 100,000 population.
Figure 39. Proportion of prior trust exposure cases, by financial year, April 2019 to March 2024 in England
Age and sex distribution
For all age and sex analyses, cases in which the age or sex was missing or recorded as unknown were excluded. In the first financial year of MSSA mandatory surveillance (FY 2011 to 2012), 265 cases (3.0%) gave the age or sex as ‘unknown’ versus 0 cases in FY 2023 to 2024.
Figure 40 compares the age and sex distribution of MSSA cases as a percentage of all reported cases in FY 2011 to 2012 and FY 2023 to 2024. Unlike MRSA, there has been no change to the distribution of cases by age and sex despite general increasing numbers of MSSA cases and increasing incidence rate.
In FY 2023 to 2024, the bulk of the burden of disease was in adults aged 45 years and over with more cases in males versus females (2.2 times more). Males see an increased burden of infection in all age groups. Furthermore, both sexes had the greatest percentage of cases among individuals aged 45 to 64 years at 18.4% and 8.5%, respectively, when compared to FY 2011 to 2012. Compared to FY 2011 to 2012, a decline was observed in those aged under 1 year for both sexes, from 2.9% to 1.4% in males and from 2.2% to 0.9% in females.
Figure 40. Age and sex distribution of MSSA bacteraemia by percentage, England, by financial years: April 2011 to March 2012 and April 2023 to March 2024
Between FY 2011 to 2012 and FY 2023 to 2024 the highest rates of MSSA incidence in males were observed among individuals aged 75 to 84 years and aged 85 years and over versus other age groups, increasing 41.8% from 74.4 to 105.5 and 54.3% from 134.5 to 207.6, respectively (Figure 41).
Similarly to males, the highest incidence rates in females between FY 2011 to 2012 and FY 2023 to 2024 were observed among individuals aged 75 to 84 years and aged 85 years and over versus other age groups, increasing 32.0% from 38.8 to 51.2 cases per 100,000 population and 32.9% from 65.6 to 87.2 cases per 100,000 population, respectively.
It should be noted that those aged under 1 year also have relatively high rates in comparison to other age groups.
Figure 41. Trends in age group and sex rates of MSSA cases, England, by financial year: April 2011 to March 2024
Note: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Trends by ethnicity
In FY 2023 to 2024, the observed incidence rate of MSSA bacteraemia was highest in the White ethnic group (24.8 cases per 100,000 population), followed by the Black and Asian ethnic groups (16.5 and 13.5 cases per 100,000 population, respectively) and lowest in the Mixed and Other ethnic groups (8.0 and 5.1 case per 100,000 population, respectively).
The age-standardised incidence rate was still highest in the White ethnic group, but we note increases in the Black and Asian ethnic groups.
Figure 42 and supplementary Table 12 in the accompanying data spreadsheet show the incidence of MSSA bacteraemia by ethnicity between April 2018 and March 2024.
Figure 42. MSSA bacteraemia rate by ethnicity, England, by financial year: April 2018 to March 2024
Note 1: shaded bands indicate 95% confidence intervals.
Note 2: mid-year population estimates for January to December 2021 onwards were unavailable at time of publication and so population data for January to December 2020 was used as a proxy.
Note 3: in FY 2020 to 2021 there was an increase in age-standardised incidence in the Asian and Black ethnic groups, mirrored by a dip in incidence in all other ethnic groups.
Trends by deprivation
In FY 2023 to 2024, 30.1 cases per 100,000 people occurred in those living in the 20% most deprived areas versus 19.3 cases per 100,000 people living in the 20% least deprived areas. The observed incidence rate of MSSA bacteraemia increased with deprivation. The general trend since April 2020 is an increase in incidence across all IMD levels, except for a recent plateau in the most deprived level.
Age-standardised incidence rates in 2023 to 2024 were greater or smaller than the observed as 36.1 and 16.8 cases per 100,000 population in the 20% most or 20% least deprived areas, respectively. The same trends in the observed incidence were mirrored in age-standardised incidence, with increased deprivation seeing increased incidence.
Figure 43 and supplementary Table 13 show the incidence of MSSA bacteraemia by deprivation between April 2018 and March 2024.
Figure 43. MSSA bacteraemia rate by deprivation, England, by financial year: April 2018 to March 2024
Note 1: shaded bands indicate 95% confidence intervals.
Note 2: mid-year population estimates for January to December 2021 onwards were unavailable at time of publication and so population data for January to December 2020 was used as a proxy.
Note 3: these differences in age-standardised incidence of MSSA bacteraemia has been consistently ordered by deprivation since April 2018.
Source of MSSA bacteraemia
The number of records reporting a source of bacteraemia has been steadily declining since the start of MSSA mandatory surveillance. In FY 2011 to 2012, a total of 3,305 (37.7%) records had entries for the source of bacteraemia. By FY 2023 to 2024, a total of 3,751 (27.8%) had entries for the source of bacteraemia.
The percentage of cases caused by skin and soft tissue infections has increased from 20.3% in FY 2011 to 2012 to 29.6% in FY 2023 to 2024. Similarly, the percentage of cases caused by pneumonia has also risen substantially from 6.0% in FY 2011 to 2012 to 12.1% in FY 2023 to 2024. The percentage of MSSA cases with catheter or line as the reported source of infection fluctuated between 13.1% and 15.7% between FY 2012 to 2013 and FY 2019 to 2020. However, since FY 2019 to 2020 the percentage of MSSA cases with catheter or line as the reported source of infection increased to 16.2% in FY 2020 to 2021 and then increased again to 17.6% in FY 2021 to 2022. The percentage of these cases has fluctuated again for FY 2023 to 2024, declining to 17.3, remaining in line with historic observations of this case burden.
Although the percentage of records for which the source of infection was not reported has increased, the percentage of cases for which the source of infection was reported as ‘unknown’ has decreased from 23.6% to 3.5% during FY 2011 to 2012 to FY 2023 to 2024. Trends in sources of MSSA bacteraemia are shown in Table 14.
Table 14. MSSA counts and rates by source of bacteraemia, England, by financial year: April 2023 to March 2024
| Financial year | Total MSSA | Source of bacteraemia reported (number) | Source of bacteraemia reported: (%) | Catheters and lines (number) | Catheters and lines (%) | Skin and soft tissue (number) | Skin and soft tissue (%) | Pneumonia (number) | Pneumonia (%) | Other (number) | Other (%) | Unknown (number) | Unknown (%) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2011 to 2012 | 8,767 | 3,305 | 37.7 | 565 | 17.1 | 670 | 20.3 | 197 | 6.0 | 1,093 | 33.1 | 780 | 23.6 |
| 2012 to 2013 | 8,812 | 3,266 | 37.1 | 492 | 15.1 | 699 | 21.4 | 232 | 7.1 | 1,088 | 33.3 | 755 | 23.1 |
| 2013 to 2014 | 9,290 | 3,236 | 34.8 | 435 | 13.4 | 684 | 21.1 | 218 | 6.7 | 1,124 | 34.7 | 775 | 23.9 |
| 2014 to 2015 | 9,863 | 3,398 | 34.5 | 445 | 13.1 | 706 | 20.8 | 305 | 9.0 | 1,087 | 32.0 | 855 | 25.2 |
| 2015 to 2016 | 10,609 | 3,224 | 30.4 | 493 | 15.3 | 769 | 23.8 | 306 | 9.5 | 1,170 | 36.3 | 487 | 15.1 |
| 2016 to 2017 | 11,499 | 3,185 | 27.7 | 500 | 15.7 | 871 | 27.3 | 365 | 11.5 | 1,280 | 40.2 | 169 | 5.3 |
| 2017 to 2018 | 11,955 | 3,529 | 29.5 | 516 | 14.6 | 1,003 | 28.4 | 445 | 12.6 | 1,440 | 40.8 | 125 | 3.5 |
| 2018 to 2019 | 12,103 | 3,732 | 30.8 | 579 | 15.5 | 1,030 | 27.6 | 450 | 12.1 | 1,595 | 42.7 | 78 | 2.1 |
| 2019 to 2020 | 12,242 | 4,152 | 33.9 | 633 | 15.2 | 1,175 | 28.3 | 503 | 12.1 | 1,729 | 41.6 | 112 | 2.7 |
| 2020 to 2021 | 11,705 | 3,565 | 30.5 | 579 | 16.2 | 968 | 27.2 | 447 | 12.5 | 1,497 | 42.0 | 74 | 2.1 |
| 2021 to 2022 | 12,306 | 3,401 | 27.6 | 600 | 17.6 | 968 | 28.5 | 352 | 10.3 | 1,391 | 40.9 | 90 | 2.6 |
| 2022 to 2023 | 13,125 | 3,267 | 24.9 | 547 | 16.3 | 976 | 29.0 | 405 | 12.0 | 1,321 | 39.3 | 114 | 3.4 |
| 2023 to 2024 | 13, 476 | 3,751 | 27.8 | 649 | 17.3 | 1,112 | 29.6 | 454 | 12.1 | 1,406 | 37.5 | 130 | 3.5 |
Note 1: financial year from April to March.
Note 2: catheters and lines include the following options from the HCAI DCS question: dialysis lines, central venous catheter (CVC) associated, peripheral venous catheter (PVC) associated and intravenous (IV) lines.
Note 3: ‘Other’ includes the following options HCAI DCS: endocarditis, osteomyelitis, other, prosthetic joint, surgical site infection (SSI), septic arthritis, urinary tract and ventilator-associated pneumonia.
Geographic distribution of MSSA bacteraemia
Regional distribution of MSSA bacteraemia cases for FY 2023 to 2024 are presented across ICB in Figure 44. It appears incidence rates of MSSA bacteraemia are similar in neighbouring ICBs, this is observed from the lowest rates to the highest. The ICBs with the highest rates were North East and North Cumbria (30.9 cases per 100,000 population), Devon ICB (30.6 cases per 100,000 population) and Cornwall and the Isles of Scilly ICB (30.4 cases per 100,000 population) reporting the highest incidence rates. In contrast, a large band of ICBs running from the West Midlands, through the Heartlands, Bedfordshire and into London have the lowest reported incidence rates. As such the lowest incidence rate were observed in the Gloucestershire ICB (14.5 cases per 100,000 population), Leicester, Leicestershire and Rutland ICB (15.8 cases per 100,000 population) and Northamptonshire ICB (15.9 cases per 100,000 population).
Figure 44. Geographic distribution of MSSA rates, England, by financial year: April 2023 to March 2024
Note: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Mortality
In FY 2023 to 2024, 13,476 MSSA bacteraemia cases were reported in England. Information on mortality was available for 98.8% (13,309) of these cases. There were 2,683 deaths within 30 days of an MSSA bacteraemia diagnosis which gave a mortality rate of 4.7 deaths per 100,000 population. CFR was calculated as 20.2%. Between FY 2022 to 2023 and FY 2023 to 2024, the trend in CFR declined from 21.9% to 20.2%. In the same period, the overall trend of mortality rate also decreased from 5.0 to 4.7 deaths per 100,000 population.
Figure 45. Case fatality rate and mortality rate of MSSA bacteraemia, England, by financial year: April 2011 to March 2024
Note: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Variation by onset of bacteraemia
The CO of mortality rate cases decreased from 3.3 to 3.0 deaths per 100,000 population (1,856 to 1,740 deaths) during FY 2022 to 2023 and FY 2023 to 2024. Similarly, the mortality rate of HO cases decreased from 2.8 to 2.6 deaths per 100,000 bed-days (979 to 943 deaths) for the same period.
Compared to the previous year, in FY 2023 to 2024, the CFR of HO and CO cases decreased from 25.5% to 24.6% and 20.4% to 18.4%, respectively.
Variation by age and sex
In FY 2023 to 2024, the mortality rate and CFR increased with age, except among children aged under one year. Mortality rate was greater in males while CFR was similar in both sexes.
The highest mortality rates in males were in those aged 85 years and over (87.8 deaths per 100,000 population) and those aged 75 to 84 years (30.4 deaths per 100,000 population) with CFRs of these age groups at 42.4% and 29.1%, respectively.
In females, the mortality rates were also higher in older age groups, 38.6 deaths per 100,000 population (aged 85 years and over) and 14.6 deaths per 100,000 population (aged 75 to 84 years). These equate to a CFR of 44.5% and 28.8% of all cases in those respective age groups.
Among children aged under one year, the mortality rate in males was 2.9 deaths per 100,000 population compared with 1.0 deaths per 100,000 population in females.
The numbers of deaths in this group are small so caution should be exercised in interpretation.
Variation by region
Case fatality rates in FY 2023 to 2024 were highest in the North East and Yorkshire (21.4%) followed by South West (21.3%) and South East (20.8%). The CFR remained lowest in London at 16.6% and East of England (19.6%).
MSSA overview of trends and discussion
The mandatory surveillance of MSSA bacteraemia was introduced in January 2011. The total number of MSSA bacteraemia has been steadily increasing throughout the 11-year surveillance period, although this trend has 2 components. Firstly, between the financial years encompassing April 2011 and March 2017 there were observed increases in community-onset bacteraemia from 5,913 to 8,401 (a 42.1% increase). The second component relates to hospital-onset infections during the time between the financial years April 2017 and March 2023. During this time the number of community-onset infections remained relatively stable while hospital-onset infections increased from 3,098 to 3,903 (26.0% increase).
In the first 2 financial years of surveillance, the MSSA bacteraemia all case rates were stable (between FY 2011 to 2012 and FY 2012 to 2013), before increasing each subsequent financial year until FY 2020 to 2021, when the rate fell from 21.7 cases per 100,000 population to 20.7 From FY 2023 to 2024 the rate has increased from 20.7 to 23.5, signifying a return to the trend seen in earlier years of surveillance. Hospital-onset rates have mostly increased annually; with a sharp rise observed between FY 2019 to 2020 and FY 2020 to 2021 from 9.6 to 12.1, respectively. Compared to FY 2020 to 2021, hospital-onset rates have seen a small reduction from 11.0 to 10.8 in FY 2023 to 2024. Concerningly, with the rise in incidence, all-cause mortality rates are also seen to be rising when compared to the pre-pandemic financial years.
Age and sex structure of MSSA bacteraemia has changed little over the time since surveillance began. The trend shows that the number and rate of infections have increased more in older age groups, particularly among males, with the highest rate seen in males aged 85 years and over. The highest all-cause mortality rates are also seen in the older aged population, particularly those aged 85 years and over, and has been rising annually. Furthermore, males also generally show higher rates of MSSA bacteraemia compared to females. However, rates of MSSA bacteraemia are also seen to be very high in the youngest age group (aged under 1 year), compared to young cases (one to 14 years old) and adults (aged 15 to 74 years).
Research using data gathered by the mandatory surveillance found that cases arising in very young cases were most likely attributable to healthcare-associated infections, rather than community-associated infections, and were related use of intravascular devices. Despite the increase in MSSA bacteraemia rates over the years, little change has been observed in the rate ratios between males and females.
Like Gram-negative and MRSA bacteraemia, those living in the most deprived areas have a disproportionately higher incidence of infection. However, age-standardised ethnicity data shows the White ethnic group to have the higher incidence, unlike the other infections described earlier.
In FY 2023 to 2024, there appears to be no similarities between the geographical distribution of MRSA and MSSA. MSSA appears to be most prevalent in the northern and south-west regions of England, while rates of MRSA bacteraemia are more evenly distributed.
As rates of MRSA continue to fall, we see the MSSA bacteraemia rates increasing to concerning rates, associated with rises in the 30-day all-cause mortality rates, although the most recent FY sees a decline. Focus needs to be shifted to better understanding the driving factors and potential interventions.
Laboratory blood cultures
On a quarterly basis NHS acute trusts are mandated to report: the total number of blood culture sets examined, the total number of these that were positive, the total number of S. aureus positive blood culture episodes and the total number of glycopeptide resistant enterococci (GRE) blood culture episodes. Below is a summary of these aggregated blood culture set results through the years for Gram-negative bacteraemia, MSSA and MRSA.
The rate of blood culture tests gradually increased between FY 2010 to 2011 and FY 2020 to 2021, rising from 46.0 to 69.4 per 1,000 bed-days. There was a decrease from FY 2020 to 2021 to 61.9 per 100,000 bed-days in FY 2021 to 2022, coinciding with the conclusion of major COVID-19 restrictions and national lockdowns. The blood culture test rate has since reverted to an upward trajectory, increasing to 66.8 per 1,000 bed-days.
Figure 46. Trends in the rate of blood culture sets, England, by financial year: April 2010 to March 2024
Epidemiological analysis of Clostridioides difficile infection (CDI)
Total reports
A total of 16,867 cases of CDI were reported by NHS acute trusts in England FY 2023 to 2024. This is an increase of 8.4% from the previous financial year (FY 2022 to 2023, n=15,563). The prevalence of CDI in England for all reported cases can be broken down into 3 distinct periods: the first between FY 2007 to 2008 and FY 2013 to 2014 is characterised by a rapid decline in the incidence rate from 107.6 cases to 24.8 cases per 100,000 population, representing a 77.0% decline; the second is one of continued gradual decline and relative stability in the incidence rate, with minimal fluctuation between FY 2013 to 2014 (24.8 cases per 100,000 population) until FY 2020 to 2021; the final period, starting in FY 2021 to 2022 sees a shift in trend for the first time since the inception of the surveillance programme, with a significant increase in cases annually, with rates reaching 29.5 infections per 100,000 population, an 8.1% annual increase in FY 2023 to 2024 from the last FY.
Overall, since the inception of mandatory CDI surveillance in FY 2007 to 2008 the total rate of CDI has decreased by 72.6%. Figure 47 shows the trends in rates of CDI cases for all cases and hospital-onset cases from FY 2007 to 2008 to FY 2023 to 2024.
Figure 47. Trends in the rate of CDI, England, by financial year: April 2007 to March 2024
Note: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Hospital and community-onset reports
Of the 16,867 total cases reported in FY 2023 to 2024, 6,760 were hospital-onset (18.8 cases per 100,000 overnight bed-days). It should be noted that CDI cases are considered hospital-onset if they occur 4 or more days after admission to an acute trust, where day of admission is day one. This data is provided for historical context only as this definition contrasts with 3 or more days for bacteraemia cases and with the definitions now imposed with the information on prior healthcare exposure for CDI.
The incidence rate for hospital-onset CDI cases mirrors the trends in incidence for all cases in the early stages of the surveillance, with a decline of 83.7% in incidence rates from FY 2007 to 2008 (89.5 cases per 100,000 overnight bed-days) to FY 2013 to 2014 (14.6 cases per 100,000 overnight bed-days). This declining trend with some fluctuations continued between FY 2013 to 2014 and FY 2018 to 2019 with the rate dropping from 14.6 to 12.2 (16.6% decrease). Following this, the rate of hospital-onset CDI cases has shifted to an upward trajectory, increasing each year consecutively from 12.2 to 18.8 cases per 100,000 bed-days, a 54.1% increase (Table 15).
The community-onset rate followed a similar epidemiological trend, with a 64.0% decline from the start of surveillance (42.8) to FY 2013 to 2014 (15.4 cases per 100,000 population). After some fluctuations the rate dropped to 14.6 in FY 2020 to 2021 and has since seen a 21.2% increase to 17.7 in FY 2023 to 2024, also shifting to an increasing year-on-year trend.
Table 15. CDI counts and rates, England, by financial year: April 2007 to March 2024
| Financial year [note 1] | Mid-year population [note 2] | All reported cases | Rate (all reported cases per 100,000 population) | Total bed-days | Hospital-onset cases | Rate (Hospital-onset cases per 100,000 bed-days) | Community-onset cases | Rate (Community-onset cases per 100,000 population) |
|---|---|---|---|---|---|---|---|---|
| 2007 to 2008 | 51,594,959 | 55,498 | 107.6 | 37,346,236 | 33,434 | 89.5 | 22,064 | 42.8 |
| 2008 to 2009 | 51,803,017 | 36,095 | 69.7 | 37,718,582 | 19,927 | 52.8 | 16,168 | 31.2 |
| 2009 to 2010 | 52,306,371 | 25,604 | 49.0 | 37,330,051 | 13,220 | 35.4 | 12,384 | 23.7 |
| 2010 to 2011 | 52,757,039 | 21,707 | 41.1 | 35,206,316 | 10,417 | 29.6 | 11,290 | 21.4 |
| 2011 to 2012 | 53,312,604 | 18,022 | 33.8 | 34,669,499 | 7,689 | 22.2 | 10,333 | 19.4 |
| 2012 to 2013 | 53,475,357 | 14,694 | 27.5 | 34,633,855 | 5,980 | 17.3 | 8,714 | 16.3 |
| 2013 to 2014 | 53,976,973 | 13,362 | 24.8 | 34,514,871 | 5,034 | 14.6 | 8,328 | 15.4 |
| 2014 to 2015 | 54,432,437 | 14,193 | 26.1 | 34,972,728 | 5,233 | 15.0 | 8,960 | 16.5 |
| 2015 to 2016 | 55,018,883 | 14,143 | 25.7 | 34,752,604 | 5,162 | 14.9 | 8,981 | 16.3 |
| 2016 to 2017 | 55,240,934 | 12,848 | 23.3 | 35,148,014 | 4,621 | 13.1 | 8,227 | 14.9 |
| 2017 to 2018 | 55,707,642 | 13,296 | 23.9 | 34,903,075 | 4,739 | 13.6 | 8,557 | 15.4 |
| 2018 to 2019 | 56,053,563 | 12,273 | 21.9 | 34,538,184 | 4,201 | 12.2 | 8,072 | 14.4 |
| 2019 to 2020 | 56,468,265 | 13,213 | 23.4 | 34,637,156 | 4,712 | 13.6 | 8,501 | 15.1 |
| 2020 to 2021 | 56,434,900 | 12,503 | 22.2 | 27,628,155 | 4,251 | 15.4 | 8,252 | 14.6 |
| 2021 to 2022 | 56,690,879 | 14,277 | 25.2 | 32,905,086 | 5,356 | 16.3 | 8,921 | 15.7 |
| 2022 to 2023 | 57,106,398 | 15,563 | 27.3 | 35,490,766 | 6,485 | 18.3 | 9,078 | 15.9 |
| 2023 to 2024 | 57,223,954 | 16,867 | 29.5 | 35,991,392 | 6,760 | 18.8 | 10,107 | 17.7 |
Note 1: financial year from April to March.
Note 2: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Prior trust exposure
The count of HOHA cases increased by 38.0% from 5,463 in FY 2017 to 2018 to 7,538 in FY 2023 to 2024. Similarly, the number of COHA cases increased by 50.0% between FY 2017 to 2018 and FY 2023 to 2024 from 1,891 to 2,836. This increase was reflected in the COHA rate, which increased 44.9% over the same period, from 4.9 to 7.1 cases per 100,000 bed-days and day admissions. COCA cases increased 64.6% in the same period from 2,858 to 4,704 cases, this corresponded to an increase of 60.8% in the rate of COCA incidence from 5.1 to 8.2 cases per 100,000 population. Counts of community-onset indeterminate association (COIA) also increased by 65.0% from 1,064 to 1,756, with an observed increase in the rate of incidence from 1.9 to 3.1 cases per 100,000 population.
Caution is advised in the interpretation of the data, as 1,758 (13%) cases were reported without prior trust exposure information in FY 2017 to 2018, before these questions were made mandatory. However, since FY 2020 to 2021, there were no cases reported without this information.
Figure 48. Proportion of prior trust exposure cases, by financial year, April 2019 to March 2024 in England
Seasonal trends in CDI
No clear trend in hospital-onset CDI (occurring in hospital admissions at NHS acute trusts on day 4 or more, where day of admissions is considered day one) has been exhibited during FY 2010 to 2011 and FY 2023 to 2024. Patterns of seasonal distribution have fluctuated: for example, in FY 2010 to 2011, 28.8% of hospital-onset cases were reported in the first quarter of the financial year (April to Jun), with declining percentages reported in the subsequent quarters of the financial year. Hospital-onset cases in FY 2011 to 2012 showed a similar distribution. However, an initial change was detected in FY 2012 to 2013 with a further shift in the distribution of CDI by financial quarter in FY 2014 to 2015 , when hospital-onset cases were more evenly distributed throughout the year. During FY 2015 to 2016 and FY 2018 to 2019, the second financial quarter of the year (July to September) saw the greatest percentage of cases reported (between 26% and 29% of cases each year), with further shifts in the distribution during FY 2019 to 2020 and FY 2023 to 2024.
In contrast, community-onset cases have always shown a peak in the second quarter of the financial year, with this quarter forming 26.6% of cases for FY 2023 to 2024.
Age and sex distribution
For all age and sex analyses, cases in which the age and or sex was missing or recorded as unknown were excluded. In FY 2007 to 2008, the age or sex was reported as unknown for 667 cases (1.2%), while in FY 2023 to 2024, the age or sex was reported as unknown for 12 cases (<1.0%).
While the number of cases has decreased dramatically over the course of CDI surveillance, there has been a subtle shift in their age and sex distribution (Figure 49) where we are seeing a higher proportion of female cases than males across all age groups except in the aged 85 years and over group.
In FY 2007 to 2008 each increasing age group contributed a higher percentage of CDI cases towards the overall burden of infection, ranging from 0.3% in those aged 2 to 14 years to 9.3% in the aged 85 years and over group in male CDI cases. In FY 2023 to 2024, the distribution in females had a marked increase in burden among the aged 2 to 14 years age group in comparison to the FY 2007 to 2008 period. Also, unlike the bacteraemias reported in this report, there is a larger percentage of cases amongst females compared to their male counterparts, for all age groups.
In FY 2023 to 2024, 1.2% of female CDI cases were among those aged 2 to 14 years versus 0.3% in FY 2007 to 2008. Similarly, female CDI cases in those aged 15 to 44 years contributed to 5.2% of the case burden in FY 2023 to 2024, a significant increase from the 2.8% reported in FY 2007 to 2008. In contrast, females aged over 85 years observed a decline in case burden from making up 20.5% of the cases (FY 2007 to 2008) to 14.6% in FY 2023 to 2024.
The distribution in males has remained more consistent between the compared financial years, although the most recent data shows an increase from 0.3% to 1.2% years in those aged 2 to 14 years, and a slight decline among those aged 75 to 84 years, from 14.5% to 13.7% between both periods.
It is important to note that this only reflects percentages of cases and that, because of the age and sex structure of the population of England, the incidence rate by age and sex can be very different.
Figure 49. Age and sex distribution of CDI by percentage, England, by financial years: April 2007 to March 2008 and April 2023 to March 2024
The rates have reduced across most age groups and for both sexes between FY 2007 to 2008 and FY 2023 to 2024. Although the largest reductions have been observed among older age groups (aged over 45 years) the exception is those aged 2 to 14 years, where a slight increase in rate has been observed in both sexes, from 4.4 to 4.7 cases per 100,000 population and 4.1 to 4.7, respectively.
In FY 2007 to 2008, the highest rate in males was 1,503.3 and 1,490.2 cases per 100,000 population in females. In FY 2023 to 2024, the highest rate remained in both sexes aged 85 years and over, but was substantially lower than FY 2007 to 2008, at 290.8 (80.7% decline) and 277.1 cases per 100,000 population (81.4% decline), respectively.
The sharp decline in the overall all case rate of CDI during FY 2007 to 2008 and FY 2013 to 2014, followed by a period of relative stability, is reflected across most age sex categories; the sharpest declines, for both sexes occurred in those aged 45 years and over. Both sexes aged over 85 years observed declines leading into FY 2020 to 2021 before increasing consecutively for the last 3 financial years. This was from 212.7 to 290.8 in males and 208.9 to 277.1 cases per 100,000 population in females in FY 2023 to 2024 (Figure 50)
Figure 50. Trends in age group and sex rates of CDI cases, England, by financial year: April 2007 to March 2024
Note: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Trends by ethnicity
In FY 2023 to 2024, the observed incidence rate of CDI was highest in the White ethnic group (32.5 cases per 100,000 population). This was followed by the Black and Asian ethnic groups (12.4 and 12.1 cases per 100,000 population, respectively), and lowest in the Mixed and Other ethnic groups (5.5 and 4.0 cases per 100,000 population, respectively).
Unlike other organisms (with the exception of MSSA), after adjusting for age, the White ethnic group remains highest at 30.2 cases per 100,000 population. However, the gap between the Black and Asian ethnic groups, and White ethnic group is much closer, with incidences at 23.0 and 23.6 cases per 100,000 population, respectively.
Figure 51 and supplementary Table 12 show the incidence of C. difficile infection by ethnicity between April 2018 and March 2024.
Figure 51. C. difficile infection rate by ethnicity, England, by financial year: April 2018 to March 2024
Note 1: shaded bands indicate 95% confidence intervals.
Note 2: mid-year population estimates for January to December 2021 onwards were unavailable at time of publication and so population data for January to December 2020 was used as a proxy.
Note 3: since FY 2020 to 2021 White, Asian and Black ethnic groups have seen sustained increases in their age-standardised incidences.
Trends by deprivation
In FY 2023 to 2024, the observed incidence rate of CDI by deprivation is broadly similar and there is a moderate relationship between incidence and increasing deprivation from 32.6 cases per 100,000 people living in the 20% most deprived areas versus 2024, 29.9 cases per 100,000 people living in the 20% least deprived areas.
However, the age-standardised incidence rates show a far stronger variation of incidence by deprivation (43.8 and 25.3 cases per 100,000 population in the 20% most and 20% least deprived areas, respectively) and sustained increases since April 2018 in all IMD levels.
Figure 52 and supplementary Table 13 show the incidence of C. difficile infection by deprivation between April 2018 and March 2024.
Figure 52. C. difficile infection rate by deprivation, England, by financial year: April 2018 to March 2024
Note 1: shaded bands indicate 95% confidence intervals.
Note 2: mid-year population estimates for January to December 2021 onwards were unavailable at time of publication and so population data for January to December 2020 was used as a proxy.
Geographic distribution of CDI
Regional distribution of cases is presented across ICB for FY 2023 to 2024. There was no clear pattern to the distribution of CDI, although there were parts of England where rates were particularly high in the Northwest, followed by East of England and parts of the Southwest (Figure 53). It was within these areas that the highest rates of CDI were observed. The 3 highest areas were Lancashire and South Cumbria ICB (46.6 cases per 100,000 population), Cornwall and the Isles of Scilly ICB (43.7 cases per 100,000 population) and Herefordshire and Worcestershire ICB (42.0 cases per 100,000 population). Conversely, parts of the Midlands leading down into London and the Southeast generally had the lowest rates of CDI. Many of the lowest incidence rates were reported from ICBs within these areas, with the 3 lowest rates being North East London ICB (15.5 cases per 100,000 population), South East London ICB (16.4 cases per 100,000 population) and North West ICB (16.8 cases per 100,000 population).
Figure 53. Geographic distribution of CDI rates, England, by financial year: April 2023 to March 2024
Note: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Mortality
In FY 2023 to 2024, 16,867 CDI cases were reported in England. Information on mortality was available for 99.3% (16,756) of these cases. There were 2,164 deaths within 30 days of a CDI, resulting in a CFR of 12.9%, which was a marginal decrease from 13.8% in FY 2022 to 2023. The mortality rate increased from 3.7 to 3.8 deaths per 100,000 population during FY 2022 to 2023 and FY 2023 to 2024.
Figure 54. Case fatality rate and mortality rate of C. difficile infection, England, by financial year: April 2007 to March 2024
Note: mid-year population estimates for January to December 2023 onwards were unavailable at time of publication and so population data for January to December 2022 was used as a proxy.
Variation by onset
The mortality rate of CO cases increased from 1.4 to 1.6 deaths per 100,000 population (828 to 912 deaths) during FY 2022 to 2023 and FY 2023 to 2024. The opposite occurred in HO cases with the mortality rate decreasing from 3.7 to 3.5 deaths per 100,000 bed-days (1,297 to 1,252 deaths) during 2022 to 2023 and FY 2023 to 2024.
The CFR of HO cases decreased from 20.2% to 18.6% between FY 2022 to 2023 and FY 2023 to 2024. CO cases also decreased from 9.2% to 9.1%.
Variation by age and sex
CDI surveillance only collects cases for those aged 2 years and over. The highest mortality rates in males were in those aged 85 years and over (70.8 deaths per 100,000 population) and in those aged 75 to 84 years (20.9 deaths per 100,000 population), with a corresponding CFR of 24.5% and 15.4%, respectively.
In FY 2023 to 2024, there was an increase in the mortality rate and a decrease in the CFR compared to FY 2022 to 2023. In those aged 85 years and over, mortality rate increased to 70.8 from 68.1 deaths per 100,000 population and CFR declined to 24.5% from 26.9%. In those aged 75 to 84 years, mortality rate declined from 21.7 to 20.9 deaths per 100,000 population and CFR from 17.8% to 15.4%.In females, the mortality rates were also higher in older age groups, 52.4 deaths per 100,000 population (aged 85 years and over) and 17.5 deaths per 100,000 population (aged 75 to 84 years). These equated to CFRs of 19.0% and 13.4% of all cases in those respective age groups.
Variation by region
Case fatality rates in FY 2023 and 2024 were highest in the North East and Yorkshire (15.2%) followed by Midlands (13.6%) and East of England (13.4%). The CFR remained lowest in London at 10.6% and South East (11.2%).
CDI overview of trends and discussion
Between FY 2007 to 2008 and FY 2013 to 2014, rates of CDI fell rapidly and since then there have been relatively stable rates of all reported cases. These sharp declines in CDI counts and rates are likely to be due to the care bundle introduced by the Department of Health and Social Care (DHSC) in 2007 which recommended the use of personal protective equipment, cohort nursing and environmental decontamination which were geared towards preventing HCAI in acute care settings and not community settings.
Despite historic declines in CDI counts and rates, FY 2023 to 2024 saw a sharp rise, marking the fourth consecutive annual increase in the hospital-onset incidence rate. This trend reflects a 54.1% increase in rate, from 12.2 to 18.8 infections per 100,000 bed-days since FY 2018 to 2019. The reasons for these increases, both in hospital- and community-onset cases, remain unclear and are under investigation. However, UKHSA data from the past 4 years show no significant changes in C. difficile ribotypes. The current hypothesis suggests that challenges in infection prevention during the pandemic, changes in antibiotic use, and improved CDI detection may be contributing factors.
Historically, CDI was primarily an issue within the hospital setting with around 60.2% of infections defined as hospital-onset (occurring on or after day 4 of an acute NHS Trust admission, where day of admission is counted as day 1). Many of the interventions aimed at the reduction of CDI rates were targeted at the hospital setting, and as a result the sharp decline that has been observed has disproportionately affected hospital-onset infections compared to community-onset infections. Consequently, community-onset cases now constitute the greater burden of all CDI for the reporting period (59.9%). However, the division of cases into hospital-onset and community-onset cases ignores the effect of any prior admissions to hospital which could increase the risk of CDI. For this reason, and to better align surveillance in England with that performed by the European Centre for Disease Prevention and Control (ECDC) and the Centres for Disease Control and Prevention (CDC), information on prior trust exposure was introduced in April 2017.
The prior trust exposure classification groups cases are based on whether a patient was admitted to the reporting organization within the past 12 weeks. To align with ECDC and CDC definitions, HOHA infections are now defined as those occurring on or after the third day of an acute NHS Trust admission, differing from the historical hospital-onset CDI classification. This classification has been in place for 6 years, with data completion improving significantly from the first to the second year due to changes in the DCS. HOHA cases formed the largest group by the new categorisation method. During FY 2023 to 2024 the number of HOHA (from 5,463 to 7,538) increased to its highest reported since the prior trust exposure surveillance began.
However, the counts of cases for community-onset groups have each increased since FY 2017 to 2018. COCA CDI cases have consistently increased year-on-year FY 2023 to 2024, by 64.6% across this time period. The underlying cause of this increase is unclear and currently under investigation. Although the prior trust exposure only records admission to the reporting organisation, work by the mandatory surveillance team using data from the Hospital Episodes Statistics estimates that this captures over 80% of all hospital interactions.
Rates of CDI are highest among older age groups, with those aged 85 years and over being the highest rates for both sexes. Research has shown that over time, elderly individuals are getting frailer and experiencing polypharmacy. A frailer population, receiving greater levels of medication would suggest that greater levels of healthcare interaction were being experienced by this age group. Despite this, the greatest reductions between the FY 2007 to 2008 and FY 2023 to 2024 in the rates of CDI have been observed in both males and females in the oldest age groups (65 years and over), although reductions have been observed across most age groups due to the large reductions observed in CDI all case counts over the course of the mandatory surveillance programme. The exception to this is in those aged 2 to 14 years, where an incremental increase in rate was observed, reflective of the increase in cases in this group. However, it should be noted, the recent rise in incidence appears to be more prominent in those aged 85 years and over, and to a lesser extent those aged 75 to 84 years.
Cases of those aged 85 years and over remain the most frequently affected by CDI and there is little difference in the rates between the sexes, although the highest incidence rates tend to be found among females. This marks a difference in epidemiology between CDI and bacteraemia in which rates are higher among male cases for most age groups.
The multiple shifts in seasonality are intriguing and currently lack an explanation. One observation is that while counts and rates were in steep decline, most hospital-onset cases occurred in the April to June quarter of the financial year. When counts and rates began to stabilise there was a shift. More investigation is required.
Previous work by this group has indicated an association between higher levels of deprivation and higher rates of CDI and historically, there has been a North-South divide in rates of CDI. However, during FY 2023 to 2024 this was not obvious. This change in the geographical distribution requires further detailed investigation.
The most deprived regions again show the highest incidence. However, unlike the other bacteraemia’s (with the exception of MSSA), the White ethnic group had the highest incidence. It should be noted that mortality rates are also rising with the rise in incidence.
Several interventions aimed at reducing MRSA rates were also aimed at reducing CDI (the ‘Clean Your Hands’ and Saving Lives campaigns). It is perhaps not surprising, then, that the trends in rates of CDI mirror those of MRSA. In addition, targets to reduce CDI cases were introduced in 2008. These aimed to reduce the number of cases reported annually to 30% of the FY 2007 to 2008 baseline count by FY 2010 to 2011, a target that was achieved by FY 2008 to 2009. In addition to the objectives and the ‘Clean Your Hands’ and Saving Lives campaigns, guidance was issued aiming to reduce clindamycin, cephalosporin or fluoroquinolone prescribing, which had been shown to promote the spread of epidemic strains of C. difficile. The resulting reduction in prescribing of fluoroquinolones and cephalosporins was associated with a significant decline in the incidence of CDI.
Laboratory stool specimens
On a quarterly basis NHS acute trusts are mandated to report; the total number of stool specimens examined, the total number of stool specimens tested for diagnosis of CDI, the total number of C. difficile toxin positive reports in people aged over 65 years, the total number of C. difficile toxin positive reports in people aged 2 to 64 years and the total number of faecal specimens and rectal swabs taken for CPE screening. Below is a summary of the toxin test results over the surveillance period for CDI.
Between FY 2010 to 2011 and FY 2013 to 2014, CDI toxin testing rates observed a decreasing trend from 18.6 per 1,000 bed days to 15.0. Since, the rate remained relatively stable until FY 2017 to 2018. After this period of stability, the rate of CDI toxin tests has increased year-on-year from 14.4 to 20.2 per 1,000 bed days in FY 2023 to 2024, becoming the highest rate of CDI toxin testing observed since the start of this data collection.
Figure 55. Trends in the rate of C. difficile toxin tests in England, by financial year: April 2010 to March 2024
Clostridioides difficile ribotyping network (CDRN)
Figure 56 below shows the total number of samples submitted to the CDRN service for ribotyping, that linked to reported mandatory surveillance CDI cases by financial year from FY 2008 to 2023.
The average annual linkage for CDI cases to CDRN cases is 29.4%. Based on this linked data, we observe steep increases in CDI isolates being submitted for ribotyping between FY 2008 to 2009 and FY 2015 to 2016 (CDRN was launched in 2007). This was followed by some fluctuations with an upward trend.
In FY 2023 to 2024, 37.7% (n=6,351) of CDI reported cases linked to CDRN cases and 33.2% had valid ribotypes. This was a substantial increase compared to the 63 cases (0.8%) that linked for FY 2008 to 2009.
Figure 56. Trends showing all linked CDRN and valid ribotypes count in England, by financial year, April 2008 to March 2024
Note: valid ribotypes are ribotypes that are recognized by the CDRN network, excluding wherever a ribotype was not available/returned (C. diff not grown isolates or duplicate request).
Figure 57 demonstrates the linked ribotypes prevalence nationally by FY 2008 to 2023. Ribotypes with a prevalence of 2% or more are shown, any valid ribotypes under 2% have been grouped into ‘Other’. The isolates assigned ‘NA’ represent sporadic ribotypes that are not commonly recognised across the CDRN labs, along with unknown and invalid data entries.
There has been a historical decline in ribotypes 001, 106 and 027 with the prevalence for 027 being under 2% in the latest FY 2023 to 2024, a steep decline from its initial prevalence of 31.7% in FY 2008 to 2009. Ribotype 106 also observes a similar trend on a smaller scale, declining from 3.2% (FY 2008 to 2009) to 2.3% in the latest financial year. In the most recent FY, 001 has seen an annual increase to 3.2% (from 2.5%), in line with its fluctuating trend.
Overall, in FY 2023 to 2024, ribotypes 015, 002, 005, 014, 023, 020, 001, 078, 106 and 050 were the most prevalent ribotypes in England (10.3%, 9.7%, 8.9%, 8.7%, 5.6%, 5.1%, 3.2%, 2.9%, 2.3% and 2.3%, respectively) during this period. With ribotypes 015, 014, 005, 002 observed as the most dominant ribotypes from FY 2012 to 2013 onwards.
The ‘Other’ ribotypes (under 2% prevalence) constituted of 29.3% of all linked ribotypes cases.
Caution should be advised when interpreting this data due to small numbers.
Figure 57. Prevalence of C.difficile ribotypes in England, by financial year April 2008 to March 2024, of linked CDRN DCS CDI cases
Future work
Over the past 4 years (FY 2019 to 2020 onwards) of mandatory surveillance, several areas of interest and research have emerged with particular focus on the changes in epidemiological trends observed during COVID-19. A summary of these trends and corresponding research is provided below.
Please note, all research is being conducted by, or in affiliation with, UKHSA colleagues.
CDI
Despite various hypotheses, the exact reasons for the unprecedented increase in hospital- and community-onset CDI cases remain unclear. Ribotypes distribution analysis has not identified a particular clonial lineage driving the increase. It is unclear the extent to which the rise in CDI cases is influenced by increasing sampling rates, as described in this report.
CDI seasonality as a result has also shifted. While rates were declining, most hospital-onset cases occurred from April to June. Now, with rising infection cases, more cases were occurring in October to December. This change may be due to increased beta-lactam prescribing to treat seasonal respiratory infections as a driver for CDI cases or due to an increase in recurrent infections.
There is a thorough investigation underway on the increase in CDI, investigating the role of co-morbidities, AMR and prescribing trends on CDI prevalence. In addition, a joint DPhil project between the National Institute for Health and Care Research (NIHR)-funded University of Oxford HPRU and UKHSA is exploring how sampling rates for CDI and E. coli influence reported infection rates, aiming to model the ‘ideal’ testing rate based on case-mix in acute NHS trusts.
Staphylococcus aureus
Incidence rates have substantially increased since FY 2020 to 2021 for MRSA and MSSA. While reduced hospital activity during FY 2020 to 2021 may have contributed, an increase in case counts has been observed in community and hospital settings. MRSA rates have been increasing since FY 2021 to 2022, exceeding pre-COVID-19 levels. MSSA rates have also risen, with community-onset cases being the driving factor. Hospital-onset cases remain elevated compared to FY 2019 to 2020. Current research focuses on investigating the rise in MSSA bacteraemia, analysing temporal trends and determining any epidemiological and clinical factors contributing to this increase. An investigation into COVID-19 co- or secondary infections is also ongoing.
Escherichia coli and Klebsiella spp.
In FY 2019 to 2020, there were significant and reductions in E. coli bacteraemia, particularly from the community setting. Investigations by the University of Oxford HPRU and UKHSA into the underlying causes of this trend are being undertaken. Bacteraemia due to Klebsiella spp. in contrast to E. coli did not see much of a decline at the start of the COVID-19 pandemic and then has increased both in terms of prevalence and AMR burden in the years following the pandemic. The reasons for the differing overarching trends in these infections is also being investigated.
There are various urinary tract infection (UTI) projects planned or underway as part of a larger UTI working group.
UKHSA are collaborating with the University of Bristol and NHS England on a 5-year NIHR funded programme titled ‘Improving Primary Care Antibiotic Prescribing to Reduce Antibiotic Resistant Urinary Tract Infections (IPAP-UTI)’. The study aims to perform Randomised Controlled Trials (RCTs) to see if primary care prescribing can influence AMR trends.
Health inequalities
Our previous Annual Epidemiological Commentary (AEC) publication (FY 2022 to 2023) was the first to include HCAI surveillance data by ethnicity and deprivation, reflecting our commitment to understanding health inequalities.
Current research at national and local levels aims to clarify how socio-economic factors, geography, ethnicity, and antimicrobial resistance influence the prevalence of Gram-negative bacteraemia, Staphylococcus aureus bacteraemia, and C. difficile infections.
There is a planned project to further investigate risk factors and other potential drivers of this disparity by ethnicity and socio-economic factors
Paediatrics
After older adults, paediatric groups, particularly males, face a significant burden from bacteraemia. Ongoing research aims to characterise the paediatric population and identify socio-economic, microbiological and clinical factors that increase the risk of these infections.
Glossary
Average
Scientifically speaking, this is a measure of location. It is a way of describing data and helps to distribute any inequalities in the data across the whole series. There are 3 main mathematical measures which can be used to calculate an ‘average’ value: the mean, mode and median. Each of these methods has their own strengths and weaknesses.
Bacteraemia
The presence of bacteria in blood.
Bias
Bias is the systematic deviation of either results or inferences from the real situation.
Confidence interval (CI)
Confidence intervals indicate the likely range in which an estimated parameter (such as a mean or rate) is likely to fall. For most scientific studies, it is impractical or impossible to measure every single member of a population and therefore the true population mean cannot be determined. Instead, a representative sample is taken, and the sample mean is used as an estimate of the population mean. Although the sample is intended to be representative, a different sample from the same population may provide a different result simply by chance. A confidence interval, over unlimited repetitions of the sample, should contain the true value of a parameter (such as the true population mean) no less than its confidence interval. It is usual to calculate the 95% confidence interval. That means that if we were to draw several independent, random samples from the same population and calculate 95% confidence intervals from each of them, then 95% of such confidence intervals would contain the true population mean. If we took 20 samples from the same population and calculated 95% confidence intervals, then 19 of 20 (95%) of these 95% confidence intervals would contain the true population meanwhile 1 of 20 (5%) will not.
Denominator
The lower portion of a rate or ratio. This should reflect the population at risk of developing a disease.
Epidemiology
Study of the occurrence and distribution of events (mostly health-related) in a population.
Gram-negative bacteria
Class of bacteria that do not retain crystal violet stain as used as part of a differential staining technique (called the Gram stain). The Gram stain is used as a way of identifying bacteria and the difference in staining results are due to differences in the bacterial cell wall, which has important implications for antimicrobial usage.
Incidence and incidence rate
New cases of a disease occurring in a study population. An incidence rate is then the number of new cases that occur in a defined population in a defined period of time.
Intensive care unit (ICU) bed-days
This is reported by units as the total number of bed days each month from patients who have spent more than 2 nights in the ICU, that is, bed days from a patient’s third night in the ICU and onwards are reported.
NHS ICBs
An administrative unit of the NHS. NHS England has 4 administrative regions: North of England, Midlands and East of England, London and South of England. Below these regions are 42 administrative geographies referred to as ICBs.
Mean
The arithmetic mean is often what people think of when they say, ‘average value’. The mean is calculated by summing all of the values in a series ( ) and then dividing by the number of values included in the series ( ). Mathematically, this is described by the following formula:
mean = (a1 + a1 + … + an) / n
A real-world example would be if you wanted to calculate the mean amount spent on food shopping over a 4-week period (that is, the average amount per week) having spent £51 in week one, £59 in week 2, £67 in week 3 and £52 in week 4:
mean cost of food per week = (£51 + £59 + £67 + £52) / 4 = £57.25
Median
The median of a series of numbers is the mid-point of that series. This provides a measure of an average value that is not overly affected by a few extreme values. The median of the following set of numbers [1, 2, 3] is 2, while the median of the set of numbers [1, 1, 1, 2, 10, 15, 16, 20, 100, 105, 110] is 15. To calculate the median value, the set of numbers needs to be arranged in order of magnitude, the median is the number that is exactly in the middle. If there is an even number of values in a set, then the median value is the arithmetic mean of the 2 central values.
Mode
Is the most frequent value in a set of data (numbers or text values), in the following set of numbers [1, 1, 1, 2, 10, 15, 16, 20, 100, 105, 110] the mode is 1 as it was included in the set 3 times, while the other numbers were only included once.
Rate ratio
Is the ratio between 2 rates. For example, if the rate of MRSA bacteraemia was 2 per 100,000 population in a year among men, and 4 per 100,000 population in a year among women, the rate ratio would be 2.0. The rate would be 2 times higher among women than men.
Methods
Inclusion criteria for reporting to the surveillance system
MRSA bacteraemia
The following positive blood cultures must be reported to UKHSA, for the mandatory MRSA surveillance: all cases of bacteraemia caused by S. aureus resistant to methicillin, oxacillin, cefoxitin or flucloxacillin.
MSSA bacteraemia
The following positive blood cultures must be reported to UKHSA, for the mandatory MSSA surveillance: all cases of bacteraemia caused by S. aureus which are susceptible to methicillin, oxacillin, cefoxitin, or flucloxacillin, that is, not subject to MRSA reporting.
E. coli bacteraemia
The following E. coli positive blood cultures must be reported to UKHSA: all laboratory confirmed cases of E. coli bacteraemia.
C. difficile infection
Any of the following defines a C. difficile infection in patients aged 2 years and over and must be reported to UKHSA:
- diarrhoea stools (Bristol Stool types 5 to 7) where the specimen is C. difficile toxin positive
- toxic megacolon or ileostomy where the specimen is C. difficile toxin positive
- pseudomembranous colitis revealed by lower gastro-intestinal endoscopy or Computed Tomography
- colonic histopathology characteristic of C. difficile infection (with or without diarrhoea or toxin detection) on a specimen obtained during endoscopy or colectomy
- faecal specimens collected post-mortem where the specimen is C. difficile toxin positive or tissue specimens collected post-mortem where pseudomembranous colitis is revealed or colonic histopathology is characteristic of C. difficile infection
Data sources and methodology
The HCAI DCS is a web portal designed by UKHSA to collect an enhanced data set.
Trusts using the website have access to all the data they have entered, which enables them to assess their burden of these HCAIs. This can be compared to a regional and national aggregate total also available to trusts from the website. Clinical commissioning groups (sub-ICBs), local authorities, ICBs, and directors of public health (DPH) are also able to register as users, allowing them to access data specific to their patients.
The data set to be collected is described in the mandatory HCAI surveillance protocol and in the case capture user guide available on the same site. Case unlocks can be requested by reporting organisations using the process described in the Unlock Requests User Guide. Revisions to data is covered by a data specific revisions and correction policy.
An R package for working with data downloaded from the DCS can be found on GitHub.
For further information on the methodology used to analyse data in this report, please refer to our QMI report.
Background information
This report
This report outlines the latest trends and developments in Gram-negative bacteraemia and C. difficile infections. It aims to provide valuable insights into the incidence, prevalence and future work related to these infections, contributing to the ongoing efforts to enhance patient safety in healthcare settings.
Throughout this report, ‘financial year’ is abbreviated to ‘FY’ and refers to the period between 1 April to 31 March in the years stated.
Prior exposure
In April 2017, the mandatory surveillance programme began capturing information on whether a patient with CDI had previously been admitted to the same reporting trust within the past 84 days (12 weeks). With the prior trust exposure, cases are split into specific groups, a full definition of these groups can be found in the glossary. Of note, unlike the bacteraemia where hospital-onset cases are the equivalent of HOHA cases, for CDI, the HOHA is based on a case being detected within a hospital stay that is at least 3 days long, with the day of admission being counted as day one, compared to the historical definition used in the hospital-onset section where the hospital stay is required to be at least 4 days long to be defined as a hospital-onset case.
In April 2019, the mandatory surveillance programme began capturing mandatory information data on whether a patient with Gram-negative and Staphylococcus aureus bacteraemia had been admitted to the same reporting trust in the previous 28 days. Cases are classified into specific ‘prior trust exposure’ groups, whose definitions can be found in the glossary.
Seasonality
Seasonality was assessed as the number of cases each quarter as a percentage of total cases for the financial year. This analysis was performed separately for hospital-onset and community-onset cases.
Further information and contact details
Feedback and contact information
To provide feedback or for any queries, contact mandatory.surveillance@ukhsa.gov.uk
Accredited official statistics
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