MOLECULAR SUBTYPING OF PREVALENT M-SEROTYPES OF STREPTOCOCCUS-PYOGENES CAUSING INVASIVE DISEASE

Reproducible methodologies and a scheme for high-resolution genotyping of Streptococcus pyogenes were defined with respect to a study of six predominant M serotypes causing invasive group,A streptococcal diseas e in the United Kingdom, Serotype reference strains were compared with nine clinical isolates of each serotype from patients with diseases s uch as pneumonia, puerperal sepsis, toxic shock-like-syndrome, celluli tis, or necrotizing fasciitis, Four enzymes were evaluated for their d iscriminatory po,ver in 16S rRNA gene-specific ribotyping. Discriminat ory power was greatest with EcoRI, which generated serotype-specific r ibotypes, and with SacI, which could subdivide strains of the same M s erotype, Twenty-five combined ribotypes were found among the 60 strain s, and the indices of discriminatory power (D values) of this method v aried from 0.51 within serotype M1 to 0.98 within strains of serotype M5, Macrorestriction with the rarely cutting endonuclease SmaI and pul sed-field gel electrophoresis gave D values varying from 0.37 within s erotype M1 to the maximal 1.0 within serotype M5, Comparison of macror estriction profiles revealed various degrees of genetic heterogeneity within M serotypes, Strains of M1, M3, M6, and M11 exhibited clonally related macrorestriction profiles, while those of R28 and M5 strains w ere consistent with polyphyletic origin.