Phage-host interactions and the production of type A streptococcal exotoxin in group A streptococci

Abstract

The infection of Streptococcus pyogenes nontoxigenic strain T253 with bacteriophage T12 to form lysogen T253 (T12) resulted in the production of type A streptococcal exotoxin (erythrogenic toxin or streptococcal pyrogenic exotoxin). Two lines of evidence indicated that lysogeny per se was not sufficient to promote toxigenic conversion of strain T253. First, a virulent mutant of phage T12, unable to form stable lysogens, was able to affect type A exotoxin production by strain T253. An unrelated virulent phage A25 did not affect type A exotoxin production after infection of strain T253. Second, the temperate phage H4489A, which established stable lysogens with strain T253, did not promote type A exotoxin production. These results suggest that there is a strain specificity to the phage-host interaction which affects type A exotoxin synthesis. Additional evidence is presented which indicates that type A streptococcal exotoxin was not a structural component of phage T12.