[Activities of antibiotics against methicillin-resistant Staphylococcus aureus with particular reference to synergetic effect between ticarcillin and fosfomycin on penicillinase non-producing methicillin-resistant S. aureus].

We tested susceptibilities of 46 strains of clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) to arbekacin (ABK), tobramycin (TOB), ticarcillin (TIPC), clavulanic acid/ticarcillin (CVA/TIPC) and fosfomycin (FOM). Twelve strains had penicillinase activity. Most strains were resistant to TOB, TIPC, FOM and CVA/TIPC, but ABK inhibited 80% of the 46 MRSA strains at a concentration of 1.56 microgram/ml. The combination of ABK and FOM was indifferent. Synergism was observed, however, between FOM and TIPC against 79% of penicillinase non-producing MRSA. This synergism may mean that FOM inhibits the production of penicillin-binding protein 2' in some strains of penicillinase non-producing MRSA.