Molecular analysis of Streptococcus pyogenes strains isolated from Chinese children with pharyngitis

Streptococcus pyogenes is an important gram-positive bacterial pathogen that causes various human diseases, of which streptococcal pharyngitis is the most common. In this work, a total of 185 S. pyogenes isolated from Chinese children with pharyngitis was analyzed by superantigen (SAg) genes, emm genotyping, and pulsed-field gel electrophoresis (PFGE). Fifty-eight (31.4%) isolates were also typed by multilocus sequence typing (MLST). The results indicate that most of the emm1 isolates possessed speA (88.5%) and speJ (83.6%), and few isolates possessed speI gene (13.1%). In contrast, none of the emm12-type isolates possessed speJ; few isolates possessed speA (5.2%); and most of the isolates possessed speI (91.7%). PFGE analysis revealed 25 different clusters, and MLST was performed for 2 predominant emm-type isolates; emm12 isolates belonged to ST36 while emm1 isolates belonged to ST28. As far as this collection is concerned, emm1 and emm12 are the prevalent genotypes among S. pyogenes strains associated with children's pharyngitis in China. Most of the pharyngitis strains can be covered by a 26-valent vaccine. A strong correspondence is found only in the direction of emm type for both SAg profiles and PFGE types but not in the reverse direction.