Biofilm formation of beta‐hemolytic group G Streptococcus dysgalactiae subspecies equisimilis isolates and its association with emm polymorphism

Biofilm formation has been well known as a determinant of bacterial virulence. Group G Streptococcus dysgalactiae subspecies equisimilis ( SDSE ), a relevant pathogen with increasing medical importance, was evaluated for the biofilm‐forming potential. Microtiter plate assay was used to assess the most feasible medium for group G SDSE to form a biofilm. Among 246 SDSE isolates examined, 46.7%, 43.5%, 33.3%, and 26.4% of isolates showed moderate or strong biofilm‐forming abilities using tryptic soy broth ( TSB ), brain heart infusion broth ( BHI ), Todd‐Hewitt broth ( THB ), and C medium with 30 mM glucose ( CMG ), respectively. The addition of glucose significantly increased the biofilm‐forming ability of group G SDSE . FCT (fibronectin–collagen–T‐antigen) typing of SDSE was first undertaken and 11 FCT types were found. Positive associations of stG10.0 or negative associations of stG245.0 , stG840.0 , and stG6.1 with biofilm‐forming ability of SDSE were, respectively, found. This was the first investigation demonstrating biofilm‐forming potential in clinical group G SDSE isolates; also, some significant associations of biofilm‐forming ability with certain emm types were presented.