Survey on resistance of the isolates of Staphylococcus aureus to Vancomycin in vitro

Objective To investigate the anti-bacterial activity of vancomycin to the isolates of Staphylococcus aureus.Methods 112 isolates of Staphylococcus aureus were isolated from various clinical specimens from Feb.2005 to Jul.2005 in our hospital.PCR was used for detecting mecA gene in Staphylococcus aureus.Posititve for mecA gene was referred as MRSA.The MICs of vancomycin were determined by agar dilution test and automated microbiology analyzer.HVRS were screened by population analysis method.Results 72 of 112(64.3%) Staphylococcus aureus were referred as MRSA.The MICs of most of them were ≤2 mg/L.MIC_(90) of vancomycin to the isolates was 2 mg/L.2 isolates grew on BHIA medium containing 2 mg/L.But they were not hVRSA.The concordance rates of the MICs of agar dilution test and automated microbiology analyzer was 35.7%.The MICS of vancomycin to 13 isolates were 4 mg/L.13 isolates above were intermediated to vancomycin NCCLS/CLSI.Conclusions Vancomycin had high anti-bacteria activity to multiresistant Staphylococcus aureus.No isolate of Staphylococcus aureus was reststant to vancomycin.Automated microbiology analyzer could not determine MICs of vancomycin to Staphylococcus aureus correctly.