Rapid and robust analytical protocol for E. coli STEC bacteria subspecies differentiation using whole cell MALDI mass spectrometry

• Published in: Talanta (Oxford) 2018-05, Vol.182, p.164-170
• Main Authors: Mclean, Kevin, Palarea-Albaladejo, Javier, Currie, Carol G., Imrie, Lisa H.J., Manson, Erin D.T., Fraser-Pitt, Douglas, Wright, Frank, Alexander, Colin J., Pollock, Kevin G.J., Allison, Lesley, Hanson, Mary, Smith, David G.E.
• Format: Article
• Language: English
• Subjects: Escherichia coli; MALDI-MS; Mass spectrometry; Shigatoxigenic E. coli; Spectral processing; STEC
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2018.01.055

Whole cell MALDI is regularly used for the identification of bacteria to species level in clinical Microbiology laboratories. However, there remains a need to rapidly characterize and differentiate isolates below the species level to support outbreak management. We describe the implementation of a modified preparative approach for MALDI-MS combined with a custom analytical computational pipeline as a rapid procedure for subtyping Shigatoxigenic E. coli (STEC) and accurately identifying strain-specifying biomarkers. The technique was able to differentiate E. coli O157:H7 from other STEC. Within O157 serotype O157:H7 isolates were readily distinguishable from Sorbitol Fermenting O157 isolates. Overall, nine homogeneous groups of isolates were distinguished, each exhibiting distinct profiles of defining mass spectra features. This offers a robust analytical tool useable in reference/diagnostic public health scenarios. [Display omitted] •Simplified preparative protocol reducing sample handling steps under containment.•Pre-processing steps to filter low quality and outlying mass spectra automatically.•Informative grouping structure of biologically relevant clusters distinguished.•Defining MS features (biomarkers) for sub-species determination and identification.•E. coli O157:H7 readily distinguished from other STEC serotypes and O157SF strains.