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

The infection of Streptococcus pyogenes nontoxigenic strain T 253 with bacteriophage T12 to form lysogen T 253 (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 T 253. First, a virulent mutant of phage T12, unable to form stable lysogens, was able to affect type A exotoxin production by strain T 253.