Superantigen genes in group A streptococcal isolates and their relationship with emm types.

Superantigens are important virulence factors in the pathogenesis of invasive disease caused by group A streptococcus (GAS). There has been a recent re-emergence of this disease worldwide. A number of novel superantigens have been described recently. This study investigated 107 isolates of GAS for possession of each of the 11 currently known superantigen genes to determine the prevalence, co-occurrence and genetic restriction amongst different emm types of GAS. The results were compared with those in previously published studies. Superantigen genes were not randomly distributed amongst GAS isolates. Certain combinations of superantigen genes were more common and the majority of emm types showed restricted superantigen profiles. This is the first prevalence study of GAS isolates to include the complete range of known superantigen genes and their restriction amongst emm types. This study contributes to the understanding of the relationship between superantigen genes and emm types, and highlights the importance of comprehensive studies in different populations.