Comparison of linezolid and vancomycin in preventing the drug resistant mutants for staphylococcus aureus.

Objective To determine the minimum inhibitory concentration(MIC),mutant prevention concentration(MPC) and selection index(SI) of linezolid and vancomycin for staphylococcus aureus in vitro and compare their capacity for restricting the selection of staphylococcus aureus resistant mutants.Methods The staphylococcus aureus strain ATCC25923 was enriched in broth,and the bacterial concentration was adjusted to 1010 colony forming units per milliliter.MIC,MPC and MPC of linezolid and vancomycin for staphylococcus aureus were determined by an agar plates dilution method,We also MPC and SI of vancomycin in combination with rifamycin and leofloxacin were determined.Results MICs of linezolid and vancomycin for staphylococcus aureus strain ATCC25923 were 1.0 and 1.0 g/L;MPCs were 6.4 and 51.2 g/L;and SIs were 6.4 and 51.2.The MPCs of vancomycin in combination with rifamycin and leofloxacin were 12.8 and 8.0 g/L, and the SIs were 25.6 and 16.0.Conclusion The capacity of linezolid for restricting the selection of staphylococcus aureus resistant mutants was stronger than that of vancomycin,and the capacity of vancomycin was raised by combining with rifamycin and leofloxacin.