Frequency of the erythrogenic toxin B and C genes (speB and speC) among clinical isolates of group A streptococci.

DNA probes corresponding to the internal region of the erythrogenic toxin B and C genes, speB and speC, were used in hybridization studies with clinical isolates of Streptococcus pyogenes to determine the frequency of occurrence of these genes in a large population of group A streptococci. More than 500 strains from different geographical locations throughout the world were used in this study. The results from colony-lift hybridization experiments indicated that the frequency of occurrence of each toxin gene among all of these strains was 100% for speB and 50% for speC. Division of these strains into subgroups of general group A strains and strains associated with scarlet fever or rheumatic fever resulted in a frequency of occurrence of speC of about 50% for all subgroups. The speC gene was found to be more frequently associated with serotype M2, M4, and M6 strains and less frequently associated with serotype M1, M3, and M49 strains. The results from a similar study with the speA gene have been previously reported (C.-E. Yu and J.J. Ferretti, Infect. Immun. 57:3715-3719, 1989).