Abstract
Lancefield group A streptococci isolated from recent outbreaks and sporadic cases of scarlet fever were restricted to the following M types 1, 3, 4, 6, 12, 18, 22 and 66. These strains were examined for the presence of streptococcal pyrogenic exotoxins (SPE) types A, B and C by isoelectric focusing in polyacrylamide gels and by immunoprecipitation in agar gels. SPE B was produced by 70% of the strains and SPE C by 40%. SPE A could not be detected in these strains. In contrast, SPE type A was found in 4 of 10 strains, held by the NCTC, that had been isolated before 1940 from patients with scarlet fever. Nine of 12 recent isolates from patients with sore throat uncomplicated by a rash produced SPE C and 4 of these also produced SPE B.