[Selection of mutant rifampin-resistant Staphylococcus aureus during the therapeutic use of this antibiotic in combinations. 3 cases].

Selection of rifampicin-resistant Staphylococcus aureus has been described in vitro and in vivo when this compound is given as monotherapy or orally. That this occurrence may be prevented by combination-antibiotic therapy is generally accepted. We report three cases of serious staphylococcal infection treated by a synergic association of rifampicin with either an aminoglycoside or vancomycin. Therapy failed as a result of selection of the same rifampicin-resistant Staphylococcus aureus (serotype and lysotype). These observations may be explained by insufficient diffusion or inactivation of the other antibiotic in the infection site.