IN-VITRO ANTIMICROBIAL EFFECTS OF VARIOUS COMBINATIONS OF PENICILLIN AND CLINDAMYCIN AGAINST 4 STRAINS OF STREPTOCOCCUS-PYOGENES

Previous studies using mouse models of Streptococcus pyogenes necrotiz ing fasciitis demonstrated that clindamycin had greater efficacy than penicillin. Frequently both agents are used concurrently in the treatm ent of severe S. pyogenes infections. This study investigated interact ions between penicillin and clindamycin. E-test and broth microdilutio n assays suggested additivity or indifference, while timed-killing ass ays demonstrated concentration-dependent variable effects. Timed-kill studies utilizing clinical concentrations suggest that there is no ant agonism with the combination of drugs but that the combination does no t have a bactericidal advantage over either penicillin or clindamycin alone.