Comparative effects of clindamycin and ampicillin on superantigenic activity of Streptococcus pyogenes.

We have tested the ability of Streptococcus pyogenes to produce streptococcal pyrogenic exotoxin A (SPEA) and superantigenic activity in the presence of sub-inhibitory concentrations of ampicillin and clindamycin. After 6 h of culture, SPEA production by S. pyogenes was higher in broths containing ampicillin (715.7 +/- 296.4 pg/10(6) cfu) than in broths containing clindamycin (167.1 +/- 31.9 pg/10(6) cfu), a difference that was not significant (P = 0.25). Promitogenic activity of bacterial supernatants was also greater in ampicillin-treated cultures (467.5 +/- 17.2 ccpm/10(6) cfu) than in clindamycin-treated cultures (169.2 +/- 8.9 ccpm/10(6) cfu), a difference that was highly significant (P = 0.0001). The data support the use of clindamycin in the treatment of streptococcal toxic shock-like syndrome, in order to inhibit superantigen synthesis.