Mutant prevention concentrations study of linezolid and vancomycin against methicillin-resistant staphylococcus aureus isolates

AIM:To compare the mutant prevention concentration(MPC)of linezolid and vancomycin against methicillin resistant staphylococcus aureus(MRSA)and study the correlation between minimal inhibitory concentration(MIC)and MPC.METHODS:MICs and MPCs of two drugs against 35 MRSA clinical stains were determined by agar plates dilution method.The correlations between MIC and MPC were determined by linear regression.The ability to restrict the resistance was evaluated according the pharmacokinetics of two drugs.RESULTS:The MPCs of two drugs against MRSA were 16 and 8 μg/mL and the MPC/MIC was 8.MPCs and MICs correlated poorly(R2 were 0.32 and 0.008,respectively).According to pharmacokinetics of two drugs,the concentration of linezolid was inside the MSW(mutant selective window)for the entire dosage interval,while the concentration of vancomycin exceeded the MPC for the most dosage interval.CONCLUSION:The capacity of vancomycin for restricting the selection of MRSA resistant mutants is stronger than that of linezolid.There is low correlation between MPC and MIC.