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

Abstract 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 emm 1 isolates possessed speA (88.5%) and speJ (83.6%), and few isolates possessed speI gene (13.1%). In contrast, none of the emm 12-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; emm 12 isolates belonged to ST36 while emm 1 isolates belonged to ST28. As far as this collection is concerned, emm 1 and emm 12 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.