Distinct cytokine-inducing ability of Streptococcus pyogenes strains isolated from toxic shock-like syndrome cases

Streptococcal toxic shock-like syndrome (TSLS) is one of the fulminant types of toxic infectious diseases caused by Streptococcus pyogenes. Although there are several candidates as the virulence factors including M protein, little is known why TSLS is caused by only some of S. pyogenes strains but not by others. In this study, we compared the cytokine inducing activity in mice between S. pyogenes M-3 type strains derived from TSLS and non-TSLS cases. After infection into mice, TSLS-derived strains persisted longer in the blood than non-TSLS-derived strains. Moreover, TSLS-derived strains were highly capable of inducing proinflammatory cytokines both in vivo and in vitro. TSLS-derived strains also showed a higher ability to produce streptolysin O (SLO). These findings suggest that SLO plays a role as a possible virulence factor accounting for the shock induction in the infected host.