Towards S. aureus maldi-typing. (c2014)

Abstract

Staphylococcus aureus is possibly the most common human pathogen causing approximately one third of all bacteria-related diseases. S. aureus’ adaptable characteristics and increasing antibiotic resistance allows it to thrive in both nosocomial and community settings. Identification of S. aureus is mainly performed via phenotypic methods and costly genotypic methods. Recently, Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) has been introduced into clinical microbiology as a means of bacterial identification to the species level. In this study, we compared MALDI protein fingerprints to genomic data of 25 S. aureus isolates, an S. epidermidis strain and an E. coli strain finding only geographic separation as visualized in a dendrogram. The absence of correlation between genomic and proteomic data to the strain level is owed to genomic mutations leading to protein isomers being falsely identified as different proteins at the MALDI level. Tryptic digests of protein extracts from one isolate were further characterized by NanoFlow Liquid Chromatography coupled with MALDI-TOF MS/MS and 94 proteins were successfully identified. Three candidate proteins are proposed for MALDI-TOF MS typing, which marks a step towards fast identification of S. aureus to the strain level via MALDI-TOF MS.