Imipenem/gentamicin and imipenem/rifampin against methicillin-resistant Staphylococcus aureus.

The combinations of imipenem with gentamicin and imipenem with rifampin were studied by the time-kill method against 20 strains of methicillin-resistant Staphylococcus aureus. Twelve strains were resistant to imipenem, 18 resistant to gentamicin, 5 resistant to both imipenem and gentamicin and 5 resistant to imipenem, gentamicin and rifampin. Imipenem/gentamicin was synergistic against 1 strain and antagonistic against another strain. Imipenem/rifampin was synergistic against 4 strains and antagonistic against 3 other strains.