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

This study compared the pathology and infection pattern of streptococcal py rogenic 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 extende d from the epidermis through the subcutaneous layers, whereas isogenic SpeB (-) variants had reduced gross pathology. At the histologic level, differen ces in necrosis and host responses to each variant were apparent. Injection of purified SpeB alone into a skin air sac failed to induce any significan t tissue damage; however, coinjection of the enzyme with either the wild-ty pe 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.