主动外排系统在耐甲氧西林金黄色葡萄球菌多重耐药中的作用

目的分析耐甲氧西林金黄色葡萄球菌（MRSA）主动外排基因（qacB、qacJ、smr），探讨其在MRSA多重耐药中的作用。方法采用计算机引物设计软件（Primer Premier 5．0）设计外排泵基因（qacB、qacJ、smr）引物，用PCR和电泳分析方法检测124株MRSA主动外排基因；用利血平进行MRSA协同抑制试验，观察其对利福平和左旋氧氟沙星药敏性的变化。结果124株MRSA中检出外排泵qacB基因86株，检出率为69．4％；qacJ基因45株，检出率为36．3％；smr基因32株，检出率为25．8％。利血平抑制实验结果显示MRSA对左旋氧氟沙星和利福平的最低抑菌浓度值下降2～32倍，表明其耐药性降低。结论MESA存在qacB、qacJ、smr等多种主动外排系统，在其多重耐药中起重要作用。

The action of active efflux system on multi-drug resistance in methicillin resistant Staphylococcus aureus

OBJECTIVE: To study the active efflux gene qacB, qacJ and smr in methicillin resistant Staphylococcus aureus (MRSA) and to investigate their effect on the multi-drug resistance (MDR) of MRSA. METHODS: The three pairs of ideal primers of active efflux gene qacB, qacJ and smr were designed by computer with Primer Premier 5.0 software. A total of 124 clinical isolates of MRSA were amplified respectively by polymerase chain reaction (PCR) with above mentioned primers. The PCR products were separated by electrophoresis on an 1.5% agarose gel with 0.5 microg/ml ethidium bronide. Reserpine inhibition test was used to observe the changes of the susceptibility to antibiotics of MRSA which had qacB, qacJ and smr genes separately. RESULTS: Of the 124 strains of MRSA, 86 strains had qacB, 45 strains had qacJ and 32 strains had smr gene. Reserpine inhibition test showed that the minimal inhibitory concentration (MIC) decreased 2 to 32 times for MRSA to levofloxacin and rifampin. CONCLUSION: MRSA have qacB, qacJ and smr active efflux systems, which play a very important role in multiple antibiotic resistance.