[Differentiation of α-hemolytic Streptococci by direct mass spectrometry profiling].

The modern phenotypic and genetic methods except for Multi Locus Sequence Typing do not allow the reliable differentiation within Mitis group of α-hemolytic streptococci. During this study the MALDI mass spectra were acquired for 28 clinical isolates initially identified as S. pneumoniae by routine bacteriological tests. Due to Multi Locus Sequence Typing these isolates were found to belong to two closely related species - S. pneumoniae (n = 22) and S. mitis (n = 6). Distribution of those isolates in accordance with cluster analysis of collected mass spectra matched to Multi Locus Sequence Typing data. The diagnostic model based on Genetic Algorithm classifier demonstrated the differentiation of α-hemolytic streptococci with 100% sensitivity and 94.6% accuracy. Statistical analysis of MS peak areas revealed 2 peaks which are different for S. mitis and S. pneumoniae groups.