First Report: Application of MALDI-TOF MS within an External Quality Assurance Exercise for the Discrimination of Highly Pathogenic Bacteria from Contaminant Flora

Abstract

In this article the authors describe the application of Matrix Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) Intact Cell Mass Spectrometry (ICMS) within a proficiency test organized by a European Union (EU)-funded project on the topic of Establishment of Quality Assurances for Detection of Highly Pathogenic Bacteria of Potential Bioterrorism Risk (EQADeBa). In total 15 samples with native bacteria, including risk group 3 (RG3) target agents and non-RG3 bacteria as potential contaminants, were analyzed by five different labs with ICMS. Whereas the technique was used by all labs and showed good performance in the identification of the non-RG3 contaminants, only one lab used mass spectrometry (MS) for RG3 identification. One reason for this restricted application of

Identification of Highly Pathogenic Microorganisms by Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry: Results of an Interlaboratory Ring Trial

“…This method does not depend on exclusive consumables and has revealed high levels of reproducibility in both intralaboratory and interlaboratory studies (28,29). Whole cells, crude cell lysates, or bacterial extracts can be utilized to generate taxon-specific fingerprint signatures (30).…”

Quality of MALDI-TOF mass spectra in routine diagnostics: results from an international external quality assessment including 36 laboratories from 12 countries using 47 challenging bacterial strains

“…In this external quality assessment (EQA), we systematically compared the MALDI-TOF MSQ between 36 routine diagnostic laboratories, using previously defined mass spectral features. EQAs on the use of MALDI-TOF MS for microbial species identification have previously been reported [22], comparing the ability of diagnostic laboratories to identify a defined set of bacterial strains using MALDI-TOF MS. As the identification results are influenced by the reference database and the MSQ, it is not possible to disentangle these two factors. We [17] and others [23] have previously shown how sample preparation adaptations can improve MSQ.…”

“…The MSQ differed between bacterial groups with a lower MSQ observed for spectra of gram-positive isolates compared to spectra of gram-negative isolates (marker masses detected: median ¼ 16; IQR ¼ [12,20] vs. median ¼ 18; IQR ¼ [15,22]; p <0.0001) (Fig. 2B).…”