[Combination effect of arbekacin and cefepime on mixed culture of MRSA and P. aeruginosa].

We investigated the in vitro combination effects of arbekacin (ABK), vancomycin (VCM) or teicoplanin (TEIC) and cefepime (CFPM) on methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa isolated from various clinical specimens. Using checkerboard titration technique by agar dilution, combinations of ABK, VCM or TEIC and CFPM exhibited synergistic effects on 25 MRSA strains. The similar effects were also observed on ABK-resistant MRSA. Combination of ABK and CFPM exhibited a good effect on P. aeruginosa, but combinations of VCM or TEIC and CFPM exhibited no synergistic effect on P. aeruginosa. In vitro bactericidal activities of ABK, VCM or TEIC and CFPM against mixed cultures of MRSA with P. aeruginosa were examined at concentration of each drug that corresponds to the serum concentration at 3 hours after the usual therapeutic dosage. VCM or TEIC alone showed bacteriostatic effects against MRSA, and no enhancements were observed when combined with CFPM. ABK alone showed good bactericidal activity against MRSA and combination with CFPM enhanced the bactericidal activity. Against P. aeruginosa, ABK or CFPM alone showed the bactericidal activity, and strong bactericidal activity was induced by the combination of ABK and CFPM. VCM and TEIC showed no bactericidal activities against P. aeruginosa. When CFPM combined with VCM or TEIC, the bactericidal activity of CFPM was not enhanced against P. aeruginosa.