title: Novel approach for differentiating Shigella species and Escherichia coli by matrix-assisted laser desorption ionization-time of flight mass spectrometry.
abstract: Shigella species are so closely related to Escherichia coli that routine matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) cannot reliably differentiate them. Biochemical and serological methods are typically used to distinguish these species; however, "inactive" isolates of E. coli are biochemically very similar to Shigella species and thus pose a greater diagnostic challenge. We used ClinProTools (Bruker Daltonics) software to discover MALDI-TOF MS biomarker peaks and to generate classification models based on the genetic algorithm to differentiate between Shigella species and E. coli. Sixty-six Shigella spp. and 72 E. coli isolates were used to generate and test classification models, and the optimal models contained 15 biomarker peaks for genus-level classification and 12 peaks for species-level classification. We were able to identify 90% of E. coli and Shigella clinical isolates correctly to the species level. Only 3% of tested isolates were misidentified. This novel MALDI-TOF MS approach allows laboratories to streamline the identification of E. coli and Shigella species.
authors.affiliation: ARUP Laboratories, Salt Lake City, Utah, USA.
authors.forename: Prasanna D
authors.initials: PD
authors.lastname: Khot
authors.forename: Mark A
authors.initials: MA
authors.lastname: Fisher
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods*; D015415:Biomarkers / Q000032:analysis; D004926:Escherichia coli / Q000737:chemistry* / Q000145:classification*; D006801:Humans; D012760:Shigella / Q000737:chemistry* / Q000145:classification*; D012984:Software; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D015415:Biomarkers