Research and analysis

HPR volume 9 issue 34: news (25 September)

Updated 29 December 2015

1. Consultation on a new microbiology test procedure using MALDI-ToF mass spectrometry

Matrix-assisted laser desorption ionization – time of flight (MALDI-ToF) mass spectrometry – a technique widely used in many clinical laboratories – is to be added to be PHE’s list of standard microbiological test methods, following publication for consultation of a new draft standard (SMI test procedure 40) by PHE’s Microbiology Services standards unit [1].

Methods currently listed under the Test Procedures category of UK Standards for Microbiology Investigations (SMIs) [2] are, for the most part, prescriptive recommendations relating to conventional laboratory procedures. The promulgation of SMI TP40 is a new departure in that, rather than providing detailed guidelines on how MALDI-ToF mass spectrometry should be carried out, it is an acknowledgement that this application of mass spectrometry – a technique traditionally applied in chemical and pharmaceutical analysis – is now in widespread use in many clinical laboratories for the identification and characterisation of microbiological pathogens.

MALDI-ToF mass spectrometry allows the analysis of biomolecules (such as DNA, proteins, peptide and sugars) and large organic molecules (such as polymers, dendrimers and other macromolecules) which tend to be fragile and fragment when ionised by more conventional ionisation methods. The technique can be used to analyse the protein composition of a microbial cell and has emerged as a new technology for species identification, particularly bacteria and fungi. It is popular because of its reproducibility, speed and sensitivity of analysis; in contrast to other identification methods, results can be available within minutes, or hours, rather than days.

Simplicity of sample preparation and the minimal costs of consumables make the method well suited for routine and high throughput use.

The draft standard includes detailed consideration of the limitations of the method, safety considerations, and the importance of related databases being maintained. Drawbacks associated with the currently available commercial platforms are acknowledged: a number of well-established commercial equipment manufacturers use their own algorithms, databases, software, and interpretive criteria for microbial identification, thereby making the data generated by these different systems not directly comparable.

The Standards Unit has invited feedback on the draft SMI test procedure before a consultation deadline of 5 October 2015.

1.1 References

1. PHE (21 September 2015). UK SMI TP 40 under consultation: Matrix assisted laser desorption ionisation time of flight mass spectrometry test procedure.

2. See: SMIs health protection collection webpages.

2. Quarterly IMD, pertussis, and COVER reports in this issue of HPR

One hundred and seventy three laboratory-confirmed cases of invasive meningococcal disease (IMD) were reported to PHE between April and June 2015, according to the latest data published in the infection reports section of this issue of HPR [1]. This represents a 20% increase over the 144 cases confirmed in the same quarter of 2014. Two hundred and seventy nine laboratory-confirmed IMD cases had been recorded in the first quarter (January to March 2015). Further analysis of the second quarter data, including breakdowns by capsular group, by laboratory testing method and by age at diagnosis is contained in the main report.

Two other second-quarter infection reports are published in this issue of HPR:

• laboratory confirmed cases of pertussis reported to the enhanced pertussis surveillance programme in England [2]
• vaccination coverage statistics for children aged up to five years in the UK (COVER programme) [3].

2.1 References

1. Laboratory confirmed reports of invasive meningococcal infections in England: April to June 2015, HPR 9(34): immunisation, 25 September 2015.
2. Laboratory confirmed cases of pertussis reported to the enhanced pertussis surveillance programme in England: January to March 2015, HPR 9(34): immunisation, 25 September 2015.
3. Quarterly vaccination coverage statistics for children aged up to five years in the UK (COVER programme): April to June 2015, HPR 9(34): immunisation, 25 September 2015.