抗MtrC单克隆抗体对淋球菌环丙沙星耐药水平的影响

目的　探讨用抗MtrC单克隆抗体（MtrC Ab）干预淋球菌多传递耐药（multiple transferable resistance, mtr）系统后，mtr主动外排泵与环丙沙星耐药的关系。方法　利用MtrC Ab、NaN3阻断mtr主动外排泵，分别测定加入和未加入阻断剂时，淋球菌对环丙沙星的吸收剩余和积累量。结果 敏感组和耐药组的吸收剩余极限分别介于70 ～ 120 ng和0 ～ 80 ng之间。未加入阻断剂时，敏感组环丙沙星积累量高于耐药组。加入MtrC Ab后，耐药组环丙沙星积累量与未加入阻断剂时敏感组无差别。加入MtrC Ab后，敏感组环丙沙星 积累量与未加入阻断剂时无差别。加入NaN3后，耐药组环丙沙星积累量与未加入阻断剂时敏感组无差别。加入NaN3后，敏感组环丙沙星积累量与未加入阻断剂时无差别。6株敏感菌均没有外排泵起作用，4 株高水平耐药菌有外排泵起作用，2 株低水平耐药菌没有外排泵起作用。结论　淋球菌外排泵主动泵出环丙沙星，导致菌体内环丙沙星积累量不足，这是引起淋球菌对环丙沙星高水平耐药的重要因素。MtrC Ab、NaN3可以阻断外排泵蛋白泵出环丙沙星，恢复淋球菌对环丙沙星的敏感性。

Effects of monoclonal antibody against MtrC on ciprofloxacin resistance level of Neisseria gonorrhoeae

Objective To study the effects of monoclonal antibody against multiple transferable resistant C （MtrC Ab） on ciprofloxacin resistance level of N.gonorrhoeae. Methods Twelve strains of N.gonorrhoeae, isolated from 1998 to 2000, were classified into resistant group and susceptible group based on their sensitivity to ciprofloxacin. MtrC Ab and NaN3 were used as inhibitors to the Mtr efflux system and added to the suspension of N.gonorrhoeae, then the quantity of ciprofloxacin uptake by and accumulation in N.gonorrhoeae was determined at 1, 5, 10, 15 and 20 minutes after the addition. Results The ciprofloxacin uptake varied between 70-120 ng and 0-80 ng in the ciprofloxacin-susceptible and -resistant group, respectively. Without inhibitors, the quantity of ciprofloxacin accumulation in the susceptible group was signifi- cantly more than that in the resistant group. After MtrC Ab or NaN3 was added, no significant changes occurred in the quantity of ciprofloxacin accumulation in either of the two groups. The Mtr efflux pump system did function in 4 strains of N.gonorrhoeae highly resistant to ciprofloxacin, but not in 6 sensitive strains or 2 strains with lower resistance. Conclusions The efflux pump system actively transfers ciprofloxacin out of the cytoplasm of N.gonorrhoeae, leading to insufficient ciprofloxacin accumulation within the bacteria, which may be an important mechanism for the resistance of N.gonorrhoeae to ciprofloxacin. MtrC Ab and NaN3 could restore the sensitivity of N.gonorrhoeae to ciprofloxacin by blocking the function of Mtr efflux pump in the bacteria.