万古霉素单用及联合用药对MRSA 耐药性的影响

目的 培养耐甲氧西林金黄色葡萄球菌（MRSA）的临床分离菌株，比较万古霉素单用与联合其他抗生素对MRSA 的影响。方法 采用琼脂平板倍比稀释法配置肉汤培养基，培养1×1010 CFU/ml 浓度的细菌，测定上述抗菌药物单用及联合使用对10 株MRSA 临床分离株的防耐药突变浓度（MPC），并计算相应的选择指数（SI）和耐药频率。结果 万古霉素单独用药组中，对MRSA 的SI 为16 ～ 64 ；万古霉素与利福平联合应用时，SI 为2 ～ 6 ；万古霉素与磷霉素联合应用时，SI 为1 ～ 8 ；并且耐药频率也呈下降趋势。结论 万古霉素分别与利福平、磷霉素联合使用，可降低其单用的MPC，缩小耐药突变选择窗，防止耐药突变菌的产生。

Effect of single use and combined use of Vancomycin on drug resistance of MRSA

Objective To culture the clinical isolates of Methicillin-resistant Staphylococcus aureus (MRSA) and compare the efficacy of single and combined use of Vancomycin against MRSA infection. Methods Agar dilution method was applied to confect broth culture medium, which was used to culture 1×1010 CFU/ml concentration of bacteria. The mutant prevention concentrations of single and combined use of Vancomycin for 10 clinical isolates of MRSA were determined, and then the corresponding selection index and the frequency of drug resistance were calculated. Results For the 10 MRSA isolates, the selection indexes of Vancomycin used alone were 16-64, the selection indexes of Vancomycin combined with Rifampicin were 2-6, and the selection indexes of Vancomycin combined with Fosfomycin were 1-8; meanwhile the frequency of drug resistance showed a downward trend. Conclusions Compared to single use, Vancomycin combined with Rifampin or Fosfomycin can reduce the mutant prevention concentration for MRSA, and narrow the drug-resistant mutant selection window, and prevent the production of drug-resistant mutant bacteria.