Virulence of two Streptococcus pyogenes strains (types M1 and M3) associated with toxic-shock-like syndrome depends on an intact mry-like gene.

The major virulence factor of Streptococcus pyogenes, the M protein, is positively regulated at the transcriptional level by mry in the M type 6 strain studied. We show here that in two S. pyogenes strains isolated from cases of toxic-shock-like syndrome, a type M1 strain and a type M3 strain, an mry-like gene is also required for resistance to phagocytosis.