Molecular subtyping of group A streptococcal strains based on virulence regulon polymorphism.

A total of 64 Streptococcus pyogenes isolates included in a previous study (Shundi et al., 2000) were further analyzed by Vir typing. Vir typing is based on restriction fragment length polymorphism (RFLP) analysis of a 4- to 8-kb pathogenicity island (vir regulon) encoding emm and other virulence genes. As all our isolates contained a single vir regulon, the stoichiometric yield of restriction fragments avoided ambiguities in interpretation of results. By using both HaeIII and HinfI restriction endonucleases to generate RFLP profiles, the 64 GAS isolates were distributed among 22 Hae- and 26 Hinf-Vir types respectively.