Transfer of group A streptococcal pyrogenic exotoxin production to nontoxigenic strains of lysogenic conversion.

Production of group A streptococcal pyrogenic exotoxins (SPE) type A and C was transferred from toxigenic streptococcal strains to nontoxigenic strains by lysogeny. Lysogens were tested for SPE with Ouchterlony immunodiffusion on Todd-Hewitt agar plates; toxin diffusing from isolated colonies reacted with specific hyperimmune antisera to SPE. Phage prepared from strains T25(3) (T12gl) and 3GL16, both yielding SPE type A, formed plaques on T25(3) (NONLYSOGENIC) lawns. Over 90% of the colonies picked from the plaque centers yielded A toxin, suggesting SPE type A was transferred by lysogenic conversion. SPE type C formation was transferred to nontoxigenic strains T25(3) and K56 with supernatant fluids from mitomycin C-induced cultures of CS112, producing SPE types B and C. All lysogens tested were positive for SPE type C, indicating that C toxin induction also was transferred by lysogenic conversion. SPE type B formation was not transferable by lysogeny with the strains tested.