Combination effect of vancomycin and cefpirome against methicillin-resistant Staphylococcus aureus in vitro--antimicrobial activities in postantibiotic phase

Abstract

The antimicrobial activities of vancomycin (VCM) or cefpirome (CPR) at sub- and above-MICs against clinical strains of methicillin-resistant Staphylococcus aureus (MRSA) during the postantibiotic phase (PAE-phase) induced by CPR or VCM were examined. Antimicrobial activities were determined growth suppression (post antibiotic sub-MIC effect: PA SME) at sub-MICs, and bactericidal activity at sub- and above-MICs. During the PAE-phase induced by VCM, growth suppression and bactericidal activity of CPR were enhanced at sub-MICs, compared with the non PAE-phase. On the other hand, during the PAE-phase induced by CPR, not only were growth suppression and bactericidal activity of VCM enhanced at sub-MICs, but bactericidal activity were enhanced at above-MICs compared with non PAE-phase. These suggest that enhancement of growth suppression and bactericidal activity during PAE-phase was a factor of combination effect of VCM and CPR against MRSA.