Combined antibacterial effects of between meropenem and vancomycin, teicoplanin, linezolid, or arbekacin in methicillin-resistant Staphylococcus aureus

In vitro interaction between meropenem(MEPM) and vancomycin(VCM), teicoplanin(TEIC), linezolid (LZD) , or arbekacin(ABK) was studied using the checkerboard technique in 207 clinical isolates of methicillin-resistant Staphylococcus aureus(MRSA) (MIC of MEPM ≧32). Of 207 strains, synergistic or additive action was observed in all strains by combination of MEPM and VCM or TEIC. A combination of MEPM and LZD or ABK showed synergistic or additive 196 strains (94.7%) and 159 strains (76.8%). Antagonism was not observed in any combination of MEPM and VCM, TEIC, or LZD, but 22 strains (10.6%) exhibited antagonism in combination with MEPM and ABK. It is thus important to know both the susceptibility of anti-MRSA agents alone and the combined effects of agents.