Susceptibility of clinical Staphylococcus aureus isolates to vancomycin.

Objective To inspect the emergence of vancomycin-resistant S.aureus(VRSA) or vancomycin-intermediate S.aureus(VISA) in Shijiazhuang.And to detect the susceptibility of vancomycin against Staphylococcus aureus(S.aureus) including methicillin-resistant S.aureus(MRSA).Methods Fifty-five S.aureus strains were isolated from clinical specimen,such as sputum,cerebrospinal fluid from two hospitals in Shijiazhuang city.Thirty strains were selected for MRSA by Kirby-Bauer disk diffusion method with oxacillin and cefoxitin out of 55 isolates and identified by latex agglutination test for the detection of penicillin-blinding protein 2a(PBP 2a).Minimal inhibitory concentration(MIC) of vancomycin against S.aureus was determined by agar dilution test.In the meantime,all the S.aureus isolated from the hospital during 2004 to 2005 were analyzed for the distribution and isolated rate of MRSA.Results MRSA and methicillin-sensitive S.aureus were all susceptible to vancomycin with a MIC ≤1 mg/L.The zone diameter of vancomycin against all 55 trains was from 15-21 mm.There was no significant difference of MIC between 30 MRSA strains and 25 MSSA strains.The occurrence of MRSA was 56.8% in 2004 and 64.5% in 2005,respectively.Conclusion VISA or VRSA are not found in the strains;however,the zone diameter and MIC value are close to the breakpoint.MRSA might not be related to the mechanism of vancomycin resistance.