Streptococcal pyrogenic exotoxin B enhances tissue damage initiated by other Streptococcus pyogenes products.

This study compared the pathology and infection pattern of streptococcal pyrogenic exotoxin B-positive (SpeB(+)) and SpeB-negative (SpeB(-)) isogenic variants of an M1 isolate of Streptococcus pyogenes in a mouse skin air sac model. SpeB(+) strains resulted in severe local tissue damage that extended from the epidermis through the subcutaneous layers, whereas isogenic SpeB(-) variants had reduced gross pathology. At the histologic level, differences in necrosis and host responses to each variant were apparent. Injection of purified SpeB alone into a skin air sac failed to induce any significant tissue damage; however, coinjection of the enzyme with either the wild-type or the speB mutant resulted in increased and accelerated tissue necrosis. Surprisingly, coinjection of the enzyme with the spleen-recovered SpeB(-) variant failed to induce a lesion.