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

Staphylococcus aureus is one of the most interesting microbial species in clinical studies. It is characterized by a wide extent of strain diversity, first of all, due to variability in virulence and pathogenicity. The aim of this study was to test the method of rapid Staphylococcus strain differentiation by a certain sign based on registration of characteristics features of MALDI mass spectra accumulated during direct protein profiling of the bacterial cell. The model signs registered as strain differences included production of β-lactamase and α-hemolysin encoded by blaZ and hla genes, respectively. The mathematical analysis of MALDI mass spectra accumulated for 53 S. aureus isolates using the clustering genetic algorithm resulted in generation of two independent classification models, which could differentiate the strains by the considered features. Using statistical contribution of each mass peak to the model, the most significant peaks (masses), which could be considered as the markers of Staphylococcus strain differences, were found. The generated diagnostic models were characterized by the following sensitivity and specificity coefficients: 97.5 and 82.5%, respectively, for strain differentiation by β-lactamase production and 90.0 and 88.7% by the presence of α-hemolysin.