[Bacteriological evaluations of combination effects with cefotiam and other antimicrobial agents against methicillin-resistant Staphylococcus aureus. II. Synergistic actions of cefotiam with arbekacin and minocycline].

We assessed the bacteriological efficacies of cefotiam (CTM) plus arbekacin (ABK) and CTM plus minocycline (MINO) therapies against methicillin-resistant Staphylococcus aureus (MRSA) in an in vitro system. The results are summarized as follows. 1. Both of CTM+ABK and CTM+MINO demonstrated almost perfect antibacterial activities against MRSA strains at ABK and MINO concentrations of MIC levels as clinically expected plasma ABK or MINO levels, and also showed antibacterial activities at ABK or MINO concentrations of sub-MIC levels. But no results suggesting antagonism were obtained. 2. The potent antibacterial effect of CTM+ABK or CTM+MINO against MRSA strains was considered to be the result of damage to the cellular membrane of target strains by ABK or MINO with ABK or MINO concentrations at MIC or sub-MIC levels and by the subsequent antibiotic effect of CTM. 3. A combination of drugs which are different from each other in mechanisms of action and points of action is likely to show a consistent antibacterial effect, but a combination of drugs which are competitive to each other because they share mechanism and point of action possibly cause antagonism.