Research and analysis

Mycoplasma genitalium Antimicrobial Resistance Surveillance (MARS) report: 2023

Updated 13 November 2024

Applies to England

This report includes sentinel Mycoplasma genitalium Antimicrobial Resistance Surveillance (MARS) data from March to June 2023.

Main findings

M. genitalium is a sexually transmitted pathogen that causes non-gonococcal urethritis (NGU) and is associated with cervicitis and pelvic inflammatory disease (PID). In 2023, the MARS programme included 928 M. genitalium specimens with linked demographic and clinical data. These showed:

• macrolide resistance of 62.2%
• fluoroquinolone resistance of 12.1%
• dual macrolide and fluroquinolone resistance of 10.1%
• most (89.6%) individuals were prescribed the recommended first or second-line treatments of azithromycin (a macrolide) or moxifloxacin (a fluoroquinolone)
• over three-quarters of individuals received doxycycline (a tetracycline) as a pre-treatment
• a high treatment success rate (95.4%) was observed with azithromycin in those with a macrolide susceptible M. genitalium infection
• a high treatment success rate (98.3%) was also seen with moxifloxacin in those with a fluoroquinolone susceptible M. genitalium infection

Recommendations

Possible cases of moxifloxacin treatment failure should be reported to the UK Health Security Agency (UKHSA) via the HIV and STI Data Exchange.

Healthcare practitioners should ensure that individuals are tested appropriately, and those diagnosed with M. genitalium are treated and managed according to national guidelines and should be alert to changes in recommended first-line therapies.

Introduction

Background

Mycoplasma genitalium is a sexually transmitted pathogen that causes NGU and is associated with cervicitis and PID. A meta-analysis of studies conducted between 1991 and 2016 found that the prevalence of M. genitalium among individuals aged 16 to 44 years was 1.3% (95% confidence interval (CI), 1.0% to 1.8%) in high-income countries and 3.9% (95% CI, 2.2% to 6.7%), in countries with lower human development indices. In the UK, the prevalence of M. genitalium infection has been reported as 1% in the general population (aged 16 to 44 years), and up to 38% in individuals attending sexual health services (SHSs).

M. genitalium is diagnosed exclusively by nucleic acid amplification tests due to difficulties in establishing in vitro culture. The limited availability of these molecular diagnostics leading to syndromic management in some settings, along with empirical treatment of NGU and other sexually transmitted infections (STIs) with azithromycin, has led to the emergence of resistant infections worldwide.

M. genitalium lacks a cell wall and is therefore inherently resistant to antibiotics that target cell wall synthesis, such as penicillin and other beta-lactams. Additionally, the organism’s substantially reduced genome further limits available targets for other antimicrobial classes. Consequently, the macrolide antibiotic azithromycin, is recommended as the first-line treatment for M. genitalium, ideally when genotypic susceptibility has been confirmed. Moxifloxacin, a broad-spectrum fluoroquinolone, is the recommended second-line treatment. Doxycycline, a second-generation tetracycline, is commonly given as pre-treatment to lower bacterial load and to increase the effectiveness of the subsequently prescribed azithromycin. Whilst genomic markers predictive of resistance to doxycycline have not been reported in M. genitalium, it is established that this bacterial species is naturally less susceptible to tetracyclines.

Macrolide resistance is conferred by a single base mutation, which inhibits antimicrobial binding, primarily at position A2058 or A2059 in region V of the 23S ribosomal ribonucleic acid (rRNA) gene (Escherichia coli numbering). The associations between 23S rRNA gene mutations and high azithromycin minimum inhibitory concentrations (MICs) and clinical treatment failure is well documented.

Fluoroquinolone resistance and clinical treatment failure is associated with mutations in the quinolone resistance determining region (QRDR) of the deoxyribonucleic acid (DNA) Topoisomerase IV subunit C (parC) gene, primarily substituting amino acids serine-83 (S83) and aspartic acid-87 (D87) (M. genitalium numbering) (1 to 3). There is limited correlation between other substitutions in ParC beyond positions S83 and D87, and moxifloxacin resistance, due to insufficient phenotypic minimum inhibitory concentration data from isolates and associated clinical outcome data. No standalone DNA Gyrase Subunit A gene (GyrA) substitutions in the QRDR have been associated with treatment failure. However, it has been demonstrated that individuals with M. genitalium with both ParC and GyrA substitutions were twice as likely to fail treatment with moxifloxacin than those with ParC substitutions alone. Of note, the ParC isoleucine83 (S83I) and GyrA M95I mutations were of particular importance.

The UKHSA performed 2 pilot collections of the MARS programme in 2019 and 2020 (4 to 5). These provided estimates of the prevalence of macrolide (69%) and fluoroquinolone resistance (8 to 11%) in M. genitalium infections, based on a limited sample size (362 and 286 specimens in 2019 and 2020, respectively).

In 2023, MARS was implemented on a larger scale at 28 SHSs and established as an annual antimicrobial resistance (AMR) sentinel surveillance programme for M. genitalium in England.

Objectives

The MARS sentinel surveillance programme aims to:

• estimate the prevalence of macrolide and fluoroquinolone resistance in M. genitalium infections in individuals attending sentinel SHSs in England
• determine the demographic, behavioural and clinical factors associated with resistance
• assess treatment outcomes of individuals diagnosed with M. genitalium

Methods

MARS sentinel surveillance programme

MARS sentinel surveillance data is obtained annually from a network of SHSs and their associated laboratories. In MARS 2023, 28 SHSs and 7 laboratories in England participated in the programme. The SHSs were recruited from 5 of the 9 UKHSA public health regions and 9 SHSs were in London (Figure 1). Testing for M. genitalium should follow the recommendations in the British Association for Sexual Health and HIV (BASHH) guidelines.

Participating laboratories were requested to store aliquots of residual M. genitalium positive specimens collected as part of routine patient care during the MARS collection period (1 March to 30 June 2023). Aliquots were assigned a unique MARS specimen ID and were stored at −20^°C prior to shipment to UKHSA via courier at the end of the collection period. Four participating laboratories routinely refer specimens to the UKHSA’s STI reference laboratory (STIRL) for M. genitalium detection and AMR testing. As such, positive specimens received during the collection period were automatically included in MARS by STIRL.

M. genitalium-positivity was confirmed using the STIRL inhouse real time-polymerase chain reaction (RT-PCR) which targets 2 intrinsic M. genitalium genes, Mycoplasma genitalium adhesin P1 (MgPa) and glyceraldehyde-3-phosphate dehydrogenase (gap).

For specimens confirmed as positive for M. genitalium, molecular antimicrobial susceptibility testing was performed via RT-PCR followed by Sanger sequencing for:

• macrolide resistance: Region V of the 23S rRNA gene
• fluoroquinolone resistance: the QRDR of the parC gene
• fluoroquinolone resistance in specimens where the parC genotype was non-wildtype: QRDR of the gyrA gene

Predicted antibiotic resistance was inferred from the detection of known M. genitalium mutations in these genes, acknowledging the limited data for correlating some QRDR mutations (Tables 2a and 2b). Sequence data was analysed using BioNumerics software (version 6.1) developed by Applied Maths.

Antimicrobial susceptibility results were securely linked to the pseudonymised GUMCAD STI Surveillance System data to obtain demographic and clinical details. GUMCAD is a disaggregated, patient-level dataset of all STI tests and diagnoses at SHSs in England. This data was further enriched with additional demographic, clinical, and behavioural information provided by SHSs through the HIV and STI Data Exchange.

The Sankey diagram was generated using the SankeyMATIC tool .

Figure 1. Map showing the 28 sentinel SHSs participating in MARS 2023 across England and London (shown at larger scale)

Source: Data from MARS sentinel surveillance programme.

Results

Sampling frame

A total of 1,289 specimens from 1,183 individuals were collected from participating SHSs and sent to STIRL (Figure 2). Most (1,106) were collected between 1 March and 30 June 2023.

Of the 1,289 specimens, 77.7% (1,001 specimens from 942 individuals) were confirmed as M. genitalium-positive using the UKHSA in-house RT-PCR assay. Discrepancies between local and STIRL M. genitalium detection results were most likely due to DNA degradation of specimens on storage, and/or disparities in assay sensitivity between commercial platforms and the STIRL in-house assay.

Among the individuals with a confirmed M. genitalium-positive specimen, 885 had a single positive specimen, 55 had 2, and 2 individuals had 3 specimens.

Almost two-thirds (65.5%; number (n) = 776 out of 1,183) of the MARS sample were linked to a GUMCAD record, providing some of the demographic data. After data cleaning, records for 1,163 individuals were successfully enhanced with additional demographic, behavioural and clinical information provided by SHS clinicians (Tables 1a to 1d).

Of the 942 individuals with a confirmed M. genitalium infection, 928 (98.5%) were eligible for inclusion after further data matching and cleaning and were therefore included in the MARS sample. Only the first specimen from an individual was included in the main analysis.

Macrolide resistance data was available for 90.6% (n = 841) of specimens; fluoroquinolone resistance data was available for 87.0% (n = 807) of specimens; and data for both were available for 83.1% (n = 772) of specimens. The gyrA genotype was investigated in 88 specimens.

Figure 2. The sentinel surveillance sampling frame flowchart in MARS 2023

Source: Data from MARS sentinel surveillance programme.

Sentinel surveillance sample

The MARS sentinel surveillance sample collects specimens from a subset of all M. genitalium diagnoses in England. Data and demographic breakdowns of all reported M. genitalium diagnoses in England are presented in the UKHSA STI annual data tables.

The MARS sentinel sample included 1,289 specimens from 1,163 patients who were diagnosed with M. genitalium at sentinel SHSs between 1 March and 30 June 2023. During the same period, 2,841 M. genitalium diagnoses were reported to GUMCAD across England, meaning the MARS 2023 sample represents 45.4% of the total national diagnoses. The sentinel nature of the MARS programme may mean the results are not representative of all M. genitalium diagnoses and AMR in M. genitalium in England.

Tables 1a and 1b show the demographic summary of 1,163 patients included in the MARS 2023 sample.

Among 1,163 individuals with a M. genitalium positive specimen, 67.9% (n = 790) were male, most of whom (69.0%) were heterosexual. Most individuals in the sentinel surveillance sample were white (50.9%), and the modal age group was aged 25 to 34 years (45.5%), with ages ranging from aged 16 to 78 years. The majority of individuals were born in the UK (67.1%; n = 738) and just over half (54.5%; n = 634) of individuals attended a SHS in London.

Among all individuals, 3.0% were living with HIV. Among those who were HIV negative, 13.7% (n = 137) were using HIV pre-exposure prophylaxis (PrEP) at the time of M. genitalium diagnosis. At diagnosis, 66.3% of individuals were symptomatic, with 78.4% of gay, bisexual, and other men who have sex with men (GBMSM) and 77.1% of heterosexual men presenting with symptoms, compared to 43.4% of women. 18.1% (n = 210) of the MARS sample were tested for M. genitalium due to being a contact, and among women this percentage was 32.6%. Among asymptomatic women, the percentage who were tested because they were a contact was 54.3% (n = 114 out of 210).

Over a third of individuals had been diagnosed with another STI in the past 12 months (33.4%), most commonly chlamydia (14.8%) or gonorrhoea (13.2%). Individuals most frequently reported having 0 to 1 (51.6%) or 2 to 5 (41.9%) sexual partners in the 3 months prior to their M. genitalium diagnosis, with 6.4% of individuals reporting having had a sexual partner outside of the UK in the same time interval.

The majority of specimens included in the sentinel surveillance sample were genital samples (87.9%), however, specimen type was not reported for 161 individuals.

Table 1a. Age, ethnic group, country of birth, and location of SHS attended among individuals included in the MARS sample, by gender and sexual orientation, 2023 [note 1]

Characteristic	GBMSM	Heterosexual men	Women [note 2]	Other [note 3]	Total
Metric	n (% of total number (N))	n (% of N)	n (% of N)	n (% of N)	n (% of N)
Number of individuals	236	545	371	11	1,163
Aged 15 to 19 years	1 (0.4%)	25 (4.6%)	28 (7.6%)	0 (0.0%)	54 (4.6%)
Aged 20 to 24 years	29 (12.3%)	133 (24.4%)	129 (34.8%)	5 (45.5%)	296 (25.5%)
Aged 25 to 34 years	99 (42.0%)	274 (50.3%)	171 (46.1%)	4 (36.4%)	548 (47.1%)
Aged 35 to 44 years	67 (28.4%)	91 (16.7%)	35 (9.4%)	1 (9.1%)	194 (16.7%)
Aged 45 years and over	40 (17.0%)	22 (4.0%)	8 (2.2%)	1 (9.1%)	71 (6.1%)
Ethnic group: Asian	25 (10.9%)	19 (3.8%)	22 (6.3%)	0 (0.0%)	66 (6.0%)
Ethnic group: black	31 (13.5%)	205 (40.6%)	55 (15.7%)	1 (9.1%)	292 (26.7%)
Ethnic group: mixed	22 (9.6%)	70 (13.9%)	33 (9.4%)	2 (18.2%)	127 (11.6%)
Ethnic group: other	14 (6.1%)	23 (4.6%)	15 (4.3%)	1 (9.1%)	53 (4.8%)
Ethnic group: white	137 (59.8%)	188 (37.2%)	225 (64.3%)	7 (63.6%)	557 (50.9%)
Ethnic group: not reported	7	40	21	0	68
Country of birth: UK	118 (52.0%)	352 (68.8%)	259 (74.0%)	9 (81.8%)	738 (67.1%)
Country of birth: outside of the UK	109 (48.0%)	160 (31.3%)	91 (26.0%)	2 (18.2%)	362 (32.9%)
Country of birth: not reported	9	33	21	0	63
Location of SHS attended: London	170 (72.0%)	301 (55.2%)	159 (42.9%)	4 (36.4%)	634 (54.5%)
Location of SHS attended: outside of London	66 (28.0%)	244 (44.8%)	212 (57.1%)	7 (63.6%)	529 (45.5%)

Source: Data from MARS sentinel surveillance programme.

Note 1: These percentages reflect the distribution of these characteristics among people attending the 28 sentinel SHSs participating in MARS.

Note 2: Includes women who have sex with men and women who have sex with women.

Note 3: Includes individuals who are gender diverse and males where sexual orientation is not reported.

Table 1b. HIV status and use of HIV PrEP among individuals included in the MARS sample, by gender and sexual orientation, 2023 [note 4]

Characteristic	GBMSM	Heterosexual men	Women [note 5]	Other [note 6]	Total
HIV status: positive	7 (1.7%)	3 (0.6%)	2 (0.6%)	1 (9.1%)	33 (3.0%)
HIV status: negative	204 (88.3%)	509 (99.4%)	339 (99.4%)	10 (90.9%)	1,062 (97.0%)
HIV status: not reported	5	33	30	0	68
Use of HIV PrEP [note 7]: no	59 (30.7%)	481 (99.8%)	318 (99.4%)	9 (90.0%)	867 (86.4%)
Use of HIV PrEP [note 7]: yes	133 (69.3%)	1 (0.2%)	2 (0.6%)	1 (10.0%)	137 (13.7%)
Use of HIV PrEP [note 7]: not reported	12	27	19	0	58

Source: Data from MARS sentinel surveillance programme.

Note 4: These percentages reflect the distribution of these characteristics among people attending the 28 sentinel SHSs participating in MARS.

Note 5: Includes women who have sex with men and women who have sex with women.

Note 6: Includes individuals who are gender diverse and males where sexual orientation is not reported.

Note 7: PrEP use is only among individuals who are HIV negative.

Table 1c. Specimen type and symptom status among individuals included in the MARS sample, by gender and sexual orientation, 2023 [note 8]

Characteristic	GBMSM	Heterosexual men	Women [note 9]	Other [note 10]	Total
Metric	n (% of N)	n (% of N)	n (% of N)	n (% of N)	n (% of N)
Number of individuals	236	545	371	11	1,163
Specimen type: genital	167 (83.1%)	386 (82.5%)	320 (98.8%)	8 (88.9%)	880 (87.9%)
Specimen type: rectal	19 (9.5%)	0 (0.0%)	2 (0.6%)	0 (0.0%)	21 (2.1%)
Specimen type: other	15 (7.5%)	82 (17.5%)	2 (0.6%)	1 (11.1%)	100 (10.0%)
Specimen type: not reported	35	77	47	2	161
Symptomatic at diagnosis: no	51 (21.6%)	125 (22.9%)	210 (56.6%)	6 (54.6%)	392 (33.7%)
Symptomatic at diagnosis: yes	18 (78.4%)	420 (77.1%)	161 (43.4%)	5 (45.5%)	771 (66.3%)

Source: Data from MARS sentinel surveillance programme.

Note 8: These percentages reflect the distribution of these characteristics among people attending the 28 sentinel SHSs participating in MARS.

Note 9: Includes women who have sex with men and women who have sex with women.

Note 10: Includes individuals who are gender diverse and males where sexual orientation is not reported.

Table 1d. Previous STI diagnosis, number of sexual partners, and sexual partners whilst abroad among individuals included in the MARS sample, by gender and sexual orientation, 2023 [note 11]

Characteristic	GBMSM	Heterosexual men	Women [note 12]	Other [note 13]	Total
Any previous STI diagnosis (last 12 months): no	93 (46.3%)	305 (70.9%)	219 (74.0%)	8 (72.7%)	625 (66.6%)
Any previous STI diagnosis (last 12 months): yes	108 (53.7%)	125 (29.1%)	77 (26.0%)	3 (27.3%)	313 (33.4%)
Any previous STI diagnosis (last 12 months): not reported	35	115	75	0	225
Previous STI diagnosis (last 12 months) [note 14]: gonorrhoea	78 (33.1%)	48 (8.8%)	27 (7.3%)	1 (9.1%)	154 (13.2%)
Previous STI diagnosis (last 12 months) [note 14]: chlamydia	53 (22.5%)	75 (13.8%)	43 (11.6%)	1 (9.1%)	172 (14.8%)
Previous STI diagnosis (last 12 months) [note 14]: syphilis	15 (6.4%)	3 (0.6%)	1 (0.3%)	0 (0.0%)	19 (1.6%)
Previous STI diagnosis (last 12 months) [note 14]: other	7 (3.0%)	20 (3.7%)	21 (5.7%)	1 (9.1%)	49 (4.2%)
Total sexual partners (past 3 months): 0 to 1	50 (23.2%)	262 (50.2%)	245 (71.4%)	6 (54.6%)	563 (51.6%)
Total sexual partners (past 3 months): 2 to 5	114 (52.8%)	248 (47.5%)	92 (26.8%)	4 (36.4%)	458 (41.9%)
Total sexual partners (past 3 months): 6 or more	52 (24.1%)	12 (2.3%)	6 (1.8%)	1 (9.1%)	71 (6.5%)
Total sexual partners (past 3 months): not reported	20	23	28	0	71
Sex partners whilst abroad (past 3 months): no	94 (87.9%)	300 (93.2%)	201 (97.1%)	6 (100.0%)	601 (93.6%)
Sex partners whilst abroad (past 3 months): yes	13 (12.2%)	22 (6.8%)	6 (2.9%)	0 (0.0%)	41 (6.4%)
Sex partners whilst abroad (past 3 months): not reported	129	223	164	5	521

Source: Data from MARS sentinel surveillance programme.

Note 11: These percentages reflect the distribution of these characteristics among people attending the 28 sentinel SHSs participating in MARS.

Note 12: Includes women who have sex with men and women who have sex with women.

Note 13: Includes individuals who are gender diverse and males where sexual orientation is not reported.

Note 14: Some individuals had more than one STI diagnosis, so appear in more than one total.

Antimicrobial resistance

Only clinical specimens that were confirmed as M. genitalium positive using the STIRL in-house assay were of sufficient yield to undergo AMR analysis. Of all sequenced specimens, 62.2% (n = 523 out of 841) had a mutation associated with macrolide resistance, most commonly A2058G (47.2%) and A2059G (44.0%) in the 23S rRNA gene (Table 2a).

Of all specimens, 12.1% (n = 98 out of 807) had an amino acid substitution predictive of fluoroquinolone resistance, most commonly consisting of serine to S83I (70.4%), followed by aspartic acid to asparagine87 (D87N) (20.4%), serine to arginine83 (S83R) (5.1%), and aspartic acid to tyrosine87 (D87Y) (4.1%). ParC substitutions other than S83I, D87N, S83R and D87Y were detected in 3.4% (n = 27) of specimens; D87G, G81C, S83N and S95N (Table 2b). These are of unknown clinical significance and are defined as non-wild-type in this report.

Predicted dual resistance to both macrolides and fluoroquinolones was detected in 10.1% (n = 78 out of 772) of specimens.

Among the 125 parC mutant specimens, sequencing of the gyrA QRDR was successful for 70.4% (n = 88). Analysis revealed mutations predictive of fluoroquinolone resistance resulting in amino acid substitutions in 5 specimens, specifically 2 methionine to isoleucine95 (M95I), 1 aspartic acid to glycine99 (D99G), 1 aspartic acid to asparagine99 (D99N), and 1 glycine to cysteine93 (G93C). Of these 5 specimens, 4 harboured a S83I ParC substitution and 1 harboured a D87N ParC substitution, all of which have been reported previously. All 5 specimens were also resistant to macrolides.

Table 2a. Frequency of mutations in the 23S rRNA gene and their association with macrolide resistance in M. genitalium specimens (n = 841)

Genotype	Frequency	Percentage (%)
Susceptible [note 15]	318	37.8%
Resistant	523	62.2%
A2058G	247	47.2%
A2058T	36	6.9%
A2059C	10	1.9%
A2059G	230	44.0%

Source: Data from MARS sentinel surveillance programme.

Note 15: Susceptible indicates wild-type sequence.

Table 2b. Frequency of amino acid substitutions in the ParC (n = 807) and GyrA (n = 88) genes and their association with fluoroquinolone resistance in M. genitalium specimens

Genotype	Frequency	Percentage (%)
ParC: susceptible [note 16]	682	84.5%
ParC: ­­­­unknown [note 17]	27	3.4%
ParC: resistant	98	12.1%
ParC: S83I	69	70.4%
ParC: S83R	5	5.1%
ParC: D87N	20	20.4%
ParC: D87Y	4	4.1%
GyrA: susceptible [note 18]	83	94.3%
GyrA: mutated	5	5.7%
GyrA: G93C	1	20.0%
GyrA: M95I	2	40.0%
GyrA: D99G	1	20.0%
GyrA: D99N	1	20.0%

Source: Data from MARS sentinel surveillance programme.

Note 16: Susceptible indicates wild-type sequence.

Note 17: Unknown includes G81C, S83N, D87G and S95N amino acid substitutions.

The percentage of specimens included in the MARS sample (2019, 2020 and 2023) that had molecular markers predictive of macrolide, fluoroquinolone, and dual resistance are presented in Figure 3. In MARS 2023, macrolide resistance decreased compared to the pilots (69.5% in 2019 and 69.1% in 2020). Fluoroquinolone resistance increased in 2023, rising from 8.4% in 2019 and 11.1% in 2020. Dual resistance remained stable compared to the 2020 pilot, in which 10.3% of sequenced specimens carried mutations associated with both macrolide and fluoroquinolone resistance. Noting that MARS 2023 has a larger sample size with additional SHSs participating.

Figure 3. The percentage of M. genitalium specimens that were macrolide, fluoroquinolone or dual macrolide and fluoroquinolone resistant (MARS 2019, 2020 and 2023)

Source: Data from MARS sentinel surveillance programme.

Resistance profiles by patient and demographic factors

The percentage of M. genitalium specimens with genotypic macrolide or fluoroquinolone resistance by selected demographics are presented in Figures 4a, 4b, 5a and 5b and Appendices Figures A1a, A1b, A2a and A2b. The following data only include specimens where macrolide (90.6%; n = 841 out of 928) or fluoroquinolone (87.0%; n = 807 out of 928) resistance data was available.

Gender and sexual orientation

The percentage of specimens with macrolide resistance was higher in GBMSM (77.4%) compared to heterosexual men (57.6%) and women (59.5%; Figure 4a). Furthermore, the percentage of specimens with an A2059G mutation was higher among GBMSM (54.2%) compared to heterosexual men (18.6%) and women (23.4%). The A2058G mutation was more common in heterosexual men (33.6%) and women (33.5%) than GBMSM (13.7%).

Although fluoroquinolone resistance was less common overall, it was higher in specimens from GBMSM (21.6%) compared to heterosexual men (9.5%) and women (9.4%; Figure 4b).

Figure 4a. Percentage of M. genitalium specimens in the MARS 2023 sentinel surveillance sample by macrolide (n = 833) resistance profile, by gender and sexual orientation

Source: Data from MARS sentinel surveillance programme.

Figure 4b. Percentage of M. genitalium specimens in the MARS 2023 sentinel surveillance sample by fluoroquinolone (n = 797) resistance profile, by gender and sexual orientation

Source: Data from MARS sentinel surveillance programme.

Age group

The percentage of specimens with macrolide resistance was similar across all age groups (ranging from 59.7% among those aged 35 to 44 years to 64.7% among those aged 45 years or over; Figure 5a). However, the distribution of macrolide resistance-associated mutations differed between age groups. The percentage of specimens with a A2058G mutation was higher among younger age groups (50.0% among those aged 15 to 19, 36.6% among those aged 20 to 24 years) compared to older age groups (11.8% among those aged 45 years and over). Conversely, the percentage of specimens with a A2059G mutation was higher in older age groups (41.2% among those aged 45 years and over; 29.8% among those aged 35 to 44 years) compared to younger age groups (13.9% among those aged 15 to 19 years).

The percentage of specimens with fluoroquinolone resistance-associated mutations varied by age group (0% in those aged 15 to 19 years compared to 14.3% in those aged 45 years and over; Figure 5b).

Figure 5a. The percentage of M. genitalium specimens in the MARS 2023 sentinel surveillance sample by macrolide (n = 841) resistance profile, by age group

Source: Data from MARS sentinel surveillance programme.

Figure 5b. The percentage of M. genitalium specimens in the MARS 2023 sentinel surveillance sample by fluoroquinolone (n = 807) resistance profile, by age group

Source: Data from MARS sentinel surveillance programme.

Previous STI in the last 12 months

When a macrolide resistance genotype result was available, previous STIs included gonorrhoea (n = 105), chlamydia (n = 115), syphilis (n = 13), and other (n = 31). There was no notable difference in the percentage of overall specimens with macrolide resistance-associated mutations in individuals with a previous STI diagnosis (62.4%) compared to those without (61.0%; Figure A1a).

The percentage of specimens with a A2059G mutation was higher among individuals with a previous STI diagnosis (32.9%) compared to those without (24.5%) whereas the percentage of specimens with a A2058G mutation was lower among individuals with a previous STI diagnosis (23.3%) compared to those without (31.0%; Figure A1a).

In those with a fluoroquinolone resistance genotype result available, previous STIs included gonorrhoea (n = 107), chlamydia (n = 115), syphilis (n = 10), and other (n = 28). The percentage of specimens with fluoroquinolone resistance-associated mutations was higher in individuals with a previous STI diagnosis (13.4%) compared to those without (10.0%; Figure A1b).

HIV Status and HIV PrEP use

The percentage of specimens with macrolide resistance-associated mutations was similar between individuals living with HIV (68.2%; n = 15 out of 22) and individuals who were HIV negative (61.8%; n = 484 out of 783; Figure A2a). Among the HIV negative group, the percentage of specimens with macrolide resistance mutations was higher among those who were using HIV PrEP at the time of M. genitalium diagnosis (83.7%; n = 82 out of 98) compared to those who were not (59.0%; n = 395 out of 671).

Additionally, the percentage of specimens with a A2059G mutation was higher among individuals living with HIV (59.1%; n = 13 out of 22) compared to those who were HIV negative (26.2%; n = 205 out of 783), although the sample size of those living with HIV was small (n = 22; Figure A2a).

Fluoroquinolone resistance-associated mutations were more common in specimens from individuals living with HIV (27.3%; n = 6 out of 22) compared to individuals who were HIV negative (11.4%; n = 85 out of 749; Figure A2b). Among those who were HIV negative, specimens from those who were using HIV PrEP at the time of M. genitalium diagnosis had a higher rate of fluroquinolone resistance (23.2%) compared to those who were not using PrEP (9.9%; Figure A2b).

Prescribing practices

Antimicrobial prescribing data was available for all individuals in the MARS 2023 sample. The Sankey diagram (Figure 6) shows the flow of all 928 patients through different M. genitalium treatment pathways.

First treatment and pre-treatment

Most individuals (89.6%; n = 831 out of 928) were prescribed the recommended first- or second-line treatments of azithromycin (n = 471) or moxifloxacin (n = 360). 39.2% of individuals prescribed azithromycin as their first treatment were infected with a macrolide-resistant strain, whereas 90.2% of individuals prescribed moxifloxacin as their first treatment were infected with a macrolide-resistant strain (where sequence data was available).

Over three-quarters of patients were initially pre-treated with doxycycline (76.1%; n = 706 out of 928). Of these, the majority proceeded to a first course of azithromycin (58.1%, (n = 410) or moxifloxacin (31.3%, n = 221). Of all patients, 6.4% (n = 59 out of 928) received only doxycycline with no further treatment.

Where doxycycline pre-treatment was not given, 5.9% (n = 55 out of 928) were prescribed azithromycin, 15.0% (n = 139 out of 928) were prescribed moxifloxacin and 1.3% (n = 12 out of 928) were prescribed other antibiotics at their first clinic attendance noted within MARS 2023. Additionally, there were 16 patients (1.7%) who did not receive any treatment.

A small number of patients were not prescribed the recommended first or second-line therapy (n = 22 out of 928, 2.4%). Of these, 13 received minocycline, 6 received pristinamycin, and 3 received metronidazole or ofloxacin. Of these patients, 10 received doxycycline pre-treatment and 12 did not. Of the 22 patients who received non first or second-line treatments, 27.3% (n = 6) had infections that were dual resistant to macrolides and fluoroquinolones. Of these 6, 4 received minocycline and 2 received pristinamycin.

Second treatment

Among patients who received azithromycin as their first treatment, the majority had no further treatment (70.3%; n = 331 out of 471). A small number of patients (3.4%; n = 16 out of 471) received a second course of azithromycin, while the majority were switched to moxifloxacin (25.1%; n = 118 out of 471). Of the patients who were switched to moxifloxacin, 92.7% (n = 102 out of 110) had a macrolide-resistant specimen (where macrolide resistance data was available).

Similarly, among those who received moxifloxacin as their first treatment, the majority also had no further treatment (90.0%, n = 324 out of 360), and the others either received a second course of moxifloxacin (5.6%; n = 20 out of 360), were switched to azithromycin (1.1%; n = 4 out of 360) or were switched to another antibiotic (3.3%; n = 12 out of 360). Of individuals who received a second treatment after moxifloxacin, 53.1% (n = 17 out of 32) had a fluoroquinolone-resistant infection (2 D87Y and 15 S83I). Of the 17 individuals with a fluoroquinolone-resistant infection, 4 of the individuals with an S83I substitution also had either a M95I (n = 2), D99G (n = 1), or D99N (n = 1) substitution in GyrA (where sequence data was available).

Third, fourth, and fifth treatments

Further courses of treatment (third and beyond) were rare and involved a small number of individuals: 33 patients received a third treatment, 5 patients received a fourth, and 2 patients received a fifth treatment. These treatments were predominantly moxifloxacin, minocycline and pristinamycin. Following these 40 treatments, 11 individuals returned a positive test of cure (TOC), and 16 individuals returned a negative TOC. A TOC was not performed for 9 individuals. No TOC information was available for 4 individuals.

Figure 6. Sankey diagram showing the number of individuals prescribed each antimicrobial (combination) as their treatment for M. genitalium infection, MARS 2023

Source: Data from MARS sentinel surveillance programme.

Resistance-associated mutations and treatment outcomes

For this analysis, a treatment failure was defined as a positive TOC following treatment, while treatment success was indicated by a negative TOC post-treatment. Treatment success was assumed in cases where: a TOC was not conducted; a TOC outcome was not available; or the patient did not undergo any further treatments. A TOC may have not been completed if the patient’s symptoms resolved.

Azithromycin

Treatment outcomes for individuals prescribed azithromycin are shown in Figure 7 (where macrolide resistance data was available). Of these individuals, a TOC result following treatment was available for 54.0% (n = 232 out of 430). A high treatment success rate was seen among patients with a macrolide-susceptible infection, with 95.4% (n = 249 out of 261) of patients having a successful or assumed successful treatment with azithromycin. Despite having a macrolide-resistant M. genitalium infection, 69.8% (n = 118 out of 169) of patients still had a successful or assumed successful treatment with azithromycin.

Figure 7. The percentages of different treatment outcomes for individuals given azithromycin for M. genitalium by macrolide resistance genotype (n = 430)

Source: Data from MARS sentinel surveillance programme.

Moxifloxacin

Treatment outcomes for individuals prescribed moxifloxacin are shown in Figure 8 (where fluoroquinolone resistance data was available and the mutation effect on fluoroquinolone resistance was known). Of these individuals, a TOC result following treatment was available for 59.3% (n = 252 out of 425). Among patients with a fluoroquinolone-resistant M. genitalium infection, 79.4% (n = 54 out of 68) had or were assumed to have successful treatment (Figure 8). In comparison, 98.3% (n = 351 out of 357) of patients with a fluroquinolone-susceptible infection had a successful or assumed successful treatment with moxifloxacin.

Figure 8. The percentages of different treatment outcomes­­­ for individuals given moxifloxacin for M. genitalium by fluoroquinolone resistance genotype (n = 425)

Source: Data from MARS sentinel surveillance programme.

Discussion

The MARS 2023 collection is the largest dataset to examine the pattern of AMR in M. genitalium in England to date, composed of data from 928 individuals from 28 different SHSs. Reporting completeness was excellent, with 100% of enhanced data forms completed by SHSs. Although the sample size was substantial and spanned 5 of the 9 UKHSA regions, there is likely some selection bias, as certain regions are under or over-represented. This is due to the fact that clinic participation was mainly based on the availability of local M. genitalium testing, rather than systematically selected to ensure representativeness.

In MARS 2023, overall macrolide resistance was high, with 62.2% of sequenced specimens containing mutations associated with macrolide resistance. Fluoroquinolone resistance was lower, but still of concern, with 12.1% of specimens with an amino acid substitution predictive of fluoroquinolone resistance. Dual resistance was detected in 10.1% of specimens. Macrolide resistance decreased in 2023 compared to the pilots (69.5% in 2019 and 69.1% in 2020) (4 and 5). Fluoroquinolone resistance increased in 2023, rising from 8.4% in 2019 and 11.1% in 2020. Dual resistance remained stable compared to the 2020 pilot, in which 10.3% of sequenced specimens carried mutations associated with both macrolide and fluoroquinolone resistance. However, the sample in MARS 2023 was larger and includes additional SHSs, so results may not be directly comparable across years.

Although macrolide resistance was universally high, specimens from GBMSM (77.4%) had higher rates of resistance compared to other demographic groups. The frequency of specific macrolide resistance associated mutations differed by gender and sexual orientation, and age group. This may be evidence of distinct sexual networks, although molecular typing would be needed to confirm this.

Resistance to fluoroquinolones also differed between demographic groups. Specimens from GBMSM had substantially higher rates of fluoroquinolone resistance (21.6%) compared to the overall rate of 12.1%. Additionally, specimens from individuals living with HIV and HIV negative individuals who were using HIV PrEP at the time of M. genitalium diagnosis (predominantly GBMSM) had 27.3% and 23.2% fluoroquinolone resistance, respectively.

Among the 5 patients who were infected with a GyrA mutated strain, 4 had a documented clinical failure following treatment with moxifloxacin and went on to receive further treatment of moxifloxacin, minocycline or pristinamycin. This aligns with data reported by Murray and others.

The vast majority of patients received the first or second-line treatments recommended by BASHH, namely azithromycin and moxifloxacin, respectively. Notably, almost all patients whose first recorded treatment in MARS was moxifloxacin were infected with a macrolide resistant strain and therefore appropriately treated. This suggests that AMR results were likely available in a timely manner to guide treatment decisions for these patients. Among the 22 patients who were prescribed alternative treatments, 6 had infections that were resistant to macrolides and fluroquinolones. However, as MARS only captures data within a 4-month period, it is unclear what previous treatments these patients may have received, or what AMR susceptibility results were available to clinicians to inform treatment decisions.

The high proportion of diagnoses in asymptomatic women may indicate testing as contacts or for a TOC, but we cannot exclude inappropriate testing that does not follow the recommendations in the BASHH guideline.

Treatment outcomes were difficult to accurately ascertain as only half of patients (53.0%) had a TOC after their initial diagnosis. Treatment success was therefore inferred from the absence of a TOC result or further treatments reported, likely over-estimating the number of individuals who cleared infection.

Almost all individuals (95.4%) infected with macrolide-susceptible M. genitalium and given azithromycin were known or assumed to have been successfully treated. Interestingly, macrolide resistance-associated mutations were not unequivocally predictive of azithromycin treatment failure; almost 70% of those with a macrolide-resistant infection were known or assumed to have been successfully treated with azithromycin. Similarly high rates of clinical cure with azithromycin among patients with a macrolide resistant infection have been reported previously.

Among individuals with a macrolide-resistant infection who were successfully treated with azithromycin, 83.1% also received doxycycline. It is therefore possible that doxycycline contributed toward successful azithromycin treatment in some cases, potentially by reducing bacterial load. However, we may have over-estimated treatment success by including those without a TOC as successfully treated.

The vast majority of individuals (98.3%) infected with fluoroquinolone-susceptible M. genitalium and given moxifloxacin were known or assumed to have been successfully treated. However, the presence of fluoroquinolone resistance-associated mutations was not a reliable determinant of moxifloxacin treatment failure; nearly 80% of those with a fluoroquinolone-resistant infection were known or assumed to have been successfully treated with moxifloxacin. This is consistent with clinical studies.

One limitation of these findings is the lack of temporal analysis in the treatment outcome data. Our analyses of treatment success considered all the treatments reported in our enhanced data collection for a patient, including those before the date of specimen collection. This means for some cases, we cannot explain the relationship between resistance and treatment failure without further information and analysis.

Conclusions

The MARS 2023 sentinel surveillance programme has provided a more comprehensive picture of the AMR landscape in M. genitalium in England through a larger sample size. The 2023 findings were consistent with previous pilot results, confirming widespread macrolide resistance and highlighting increasing rates of both fluoroquinolone and dual resistance.

Notably, however, many infections that exhibited resistance appeared to be successfully treated with the corresponding antimicrobial. MARS 2023 also collected detailed demographic data, allowing for comparison of AMR rates within different population groups.

We aim to build on the 2023 findings by establishing MARS as a routine annual programme, allowing for the longitudinal monitoring of AMR in M. genitalium, providing a clearer understanding of resistance trends over time, and supporting the development of effective treatment guidelines and public health strategies.

Appendices

Figure A1a. The percentage of M. genitalium specimens in the MARS 2023 sentinel surveillance sample by macrolide (n = 805 and n = 744) resistance profile, by HIV status and HIV PrEP use

Source: Data from MARS sentinel surveillance programme.

Figure A1b. Percentage of M. genitalium specimens in the MARS 2023 sentinel surveillance sample by fluoroquinolone (n = 771 and n = 710) resistance profile, by HIV status and HIV PrEP use

Source: Data from MARS sentinel surveillance programme.

Figure A2a. The percentage of M. genitalium specimens in the MARS 2023 sentinel surveillance sample by macrolide (n = 684) resistance profile, by previous STI in the last 12 months

Source: Data from MARS sentinel surveillance programme.

Figure A2b. Percentage of M. genitalium specimens in the MARS 2023 sentinel surveillance sample by fluoroquinolone (n = 657) resistance profile, by previous STI in the last 12 months

Source: Data from MARS sentinel surveillance programme.

Ethnic categories

The ethnic categories used in this report are as specified by the Office for National Statistics. The ethnicities included in each of the aggregated ethnic groups are presented below.

List of ethnicities by ethnic category

White:

• British
• Irish
• any other white background

Mixed:

• white and Black Caribbean
• white and Black African
• white and Asian
• any other mixed background

Asian or Asian British:

• Indian
• Pakistani
• Bangladeshi
• Chinese
• any other Asian background

Black or black British:

• Caribbean
• African
• any other black background

Other ethnic groups:

• any other ethnic group

References 

1. T Deguchi, SI Maeda, M Tamaki, T Yoshida, H Ishiko, M Ito, S Yokoi, Y Takahashi and S Ishihara. ‘Analysis of the gyrA and parC genes of mycoplasma genitalium detected in first-pass urine of men with non-gonococcal urethritis before and after fluoroquinolone treatment’ Journal of Antimicrobial Chemotherapy 2001, volume 48, issue 5, pages 742 to 744 (accessed on 7 November 2024)

2. G L Murray, C S Bradshaw, M Bissessor, J A Danielewski, S M Garland, J S Jensen, C K Fairley and S N Tabrizi. ‘Increasing macrolide and fluoroquinolone resistance in mycoplasma genitalium’ Emerging Infectious Diseases 2017, volume 23, issue 5, pages 809 to 812 (accessed on 7 November 2024)

3. R Hamasuna, P T Le, S Kutsuna, K Furubayashi, M Matsumoto, N Ohmagari, N Fujimoto, T Matsumoto and J S Jensen. ‘Mutations in parC and gyrA of moxifloxacin-resistant and susceptible mycoplasma genitalium strains’ PLOS ONE 2018, volume 13, issue 6, article e0179572 (accessed on 7 November 2024)

4. H Fifer, R Merrick, R Pitt, M Yung, H Allen, M Day, K Sinka, N Woodford, H Mohammed, C, S Brown, G Hughes and M Cole. ‘Frequency and correlates of mycoplasma genitalium antimicrobial resistance mutations and their association with treatment outcomes: findings from a National sentinel surveillance pilot in England Sexually Transmitted Disease’ Journal of the American Sexually Transmitted Disease Association 2021, volume 48, issue 12, pages 951 to 954 (accessed on 7 November 2024)

5. Q Enayat, R Merrick, R Pitt, M Day, J Minshull, K Sinka, K Folkard, N Woodford, C Brown, H Mohammed, M Cole and H Fifer. ‘Mycoplasma genitalium antimicrobial resistance Surveillance (MARS) second pilot report’ UK Health Security Agency 2021 (accessed on 7 November 2024)

Acknowledgements 

The MARS Team would like to thank the collaborating centres for their continued support, SHSs for the prompt submission of clinical data and laboratories for sending isolates to the national STI reference laboratory at the UKHSA, Colindale.

Collaborating centres

• 10 Hammersmith Broadway (TS Carvalho, M Rayment, Y Walters)
• Archway Sexual Health Clinic and Mortimer Market Centre (R Browne, E McGloughlin, B Singh)
• Barking Community Hospital (A Umaipalan, M Williamson, S Obeyesekera)
• Burrell Street Sexual Health Clinic (A Nori)
• Cambridgeshire Community Services NHS Trust integrated Contraception and Sexual Health (S Edwards, M Raychaudhuri, S Basavaraj, I Hawkins, E Hodges, D Alresheidat, H Pintilie, K Mariyappa, N David, R Acosta, R Moussa, C Sewell, D Johnson, D Raha, H Pollitt)
• Dean Street Clinic (G Whitlock, N Girometti, S Patel, A McOwan, F Lander)
• Derwent and Solway Clinics (A Hodgson)
• Homerton Hospital (P Horne)
• Jefferiss Wing Centre for Sexual Health (R Dawson, K Poon, G Garcia)
• Royal Liverpool University Hospital (A Elmer, G Tyson, G McCarthy, M Wood, P Cochrane, B Harrison, E Clarke)
• Royal Sussex County Hospital (S Soni)
• The Hathersage Centre (S Buckley)
• The Royal London (S Singh)
• University Hospital Birmingham (J Phattey)

Authors: Kirsty Bennet, James Johnson, Rachel Pitt-Kendall, Sandra David, Michaela Day, Fahima Rashid, Emma Callan, Michelle Cole, Suzy Sun, Prarthana Narayanan, Katie Thorley, Hamish Mohammed, Katy Sinka, Sarah Alexander, Helen Fifer.

Suggested citation

Bennet KF, Johnson J E C, Pitt-Kendall R, David S, Day MJ, Rashid F, Callan E, Cole MJ, Sun S, Narayanan P, Thorley K, Mohammed H, Sinka K, Alexander S, Fifer H, and contributors. Antimicrobial resistance in M. genitalium in England. Mycoplasma genitalium Antimicrobial Resistance Surveillance (MARS) report: 2023. November 2024, UKHSA, London.