The antimicrobial activity of rifampin: emphasis on the relation to phagocytes.

Rifampin appears to be a uniquely effective antibiotic for the treatment of certain infections. Only rifampin, of nine antimicrobial agents studied, killed staphylococci inside polymorphonuclear neutrophils or Escherichia coli inside macrophages. Rifampin, unlike penicillin, penetrated living, intact neutrophils. Rifampin was more effective than other antistaphylococcal antibiotics for the treatment of staphylococcal infections induced by subcutaneous, intraperitoneal, or intravenous injection of the organisms into mice. Rifampin-resistant variants occur in low numbers among clinical isolates (frequency, 10(-8)), and some of these variants are diminished in virulence for mice. Treatment of infected mice with rifampin plus another antimicrobial agent prevented the emergence of resistant variants. Thus, there is firm in vitro and in vivo support for studies of the clinical efficacy of rifampin for staphylococcal infections.