[Strain differentiation of Staphylococcus aureus by means of direct MALDI TOF mass spectrometry profiling]

Staphylococcus aureus--one of the most interesting for clinical studies of microbial species with extensive strain diversity, primarily due to the variability of virulence factors and pathogenicity. The aim of this study was approbation of a method for the rapid strain differentiation of S. aureus on the basis of bacterial cell direct protein profiling approach by means of MALDI TOF MS. Beta-lactamase and alpha-hemolysin productions, cording by the blaZ and hla genes, respectively, were selected as markers for the strain differentiation. Mathematical analysis of MALDI mass spectra from 53 isolates allowed the construction of two independent classification models that can differentiate the strains on the presence/absence of blaZ or hla genes. A number of the most significant peaks (masses), which can be considered as markers of the strain differences in S. aureus, were identified using a statistical contribution of each mass peak in the models. These diagnostic models differ the sensitivity and the specificity, which were 97.5% and 82.5% for the classification of strains on the basis of beta-lactamase production, and 90.0% and 88.7% by the presence of alpha-hemolysin.