环丙沙星联合阿米卡星降低环丙沙星对鲍曼不动杆菌耐药突变选择窗的体内研究

Joint application of ciprofloxacin and amikacin on mutant selective windows of the ciprofloxacin against Acinetobacter baumannii

目的在动物体内观察环丙沙星联合阿米卡星，能否缩小环丙沙星对鲍曼不动杆菌的耐药突变选择窗。方法体外测定环丙沙星与阿米卡星对鲍曼不动杆菌标准菌株ATCCl9606的最低抑菌浓度、防耐药突变浓度、并计算突变选择指数；高效液相色谱法测定环丙沙星在兔组织液中药代动力学参数。建立55只兔组织笼感染模型，随机分为11组，1组为生理盐水组f对照组），5组单用环丙沙星（环丙沙星组），5组为环丙沙星联合阿米卡星组。环丙沙星每次给药间隔2h，连续给药10次，使兔组织液环丙沙星稳态浓度分别均达No．5、1．0、2．0、4．0和8．0mg／L浓度；阿米卡星4mg／（kg·d），其组织液浓度在5～20mg／L，恰好在MSW内。3d后抽取组织液，涂布于含有0．5mg／L浓度环丙沙星的琼脂平板，有细菌生长者为耐药突变体。结果体外环丙沙星与阿米卡星对鲍曼不动杆菌的MIC、MPC及S1分别为0．5mg／L、8mg／L、16与4．0mg／L、64mg／L、16。环丙沙星组：环丙沙星浓度0．5、1．0、2．0及4．0mg／L亚组家兔组织液中均有耐药突变体的生长，8．0mg／L亚组没有耐药突变体生长；即体内环丙沙星MPC与体外相同，SI为16。联合组：环丙沙星浓度0．5和1．0mg／L亚组有耐药突变体生长，2．0、4．0及8．0mg／L亚组没有耐药突变体的生长，即联合阿米卡星后环丙沙星的MPC为2．0mg／L，联合后MIC为0．25mg／L，因此SI为8。结论环丙沙星联合阿米卡星可以缩小环丙沙星对鲍曼不动杆菌的耐药突变选择窗，从而减少耐药突变体的产生，有利于减少细菌耐药。

Objective To observe whether the mutant selective windows （MSW） of ciprofloxacin will reduce after combining amikacin against Acinetobacter baumannii in rabbit. Methods First, minimal inhibitory concentration（MIC）, mutant prevention concentration （MPC）, mutant selective windows （MSW, MPC-MIC） and selective index（SI, MPC/MIC） of ciprofloxacin and amikacin respectively with standard strain ATCC19606 were measured in vitro. The rabbit tissue cage model was constructed, and the pharmacokinetic parameters in rabbit of ciprofloxacin by high performance liquid chromatography was determined. Fifty-five rabbits were randomly divided into eleven groups by random number table. One group was used physiological saline. Five groups were used ciprofioxacin single; Other five groups were applied ciprofloxacin combined amikacin. Give the rabbits ciprofloxacin 10 times a day with a 2-hours dosing interval. Both single and combined groups, the steady state concentrations of ciprofloxacin reached to 0.5, 1.0, 2.0, 4.0 and 8.0mg/L respectively. The dose of amikacin was 4mg/（kg.d）, and its peakconcentration get to 5-20mg/L probably and in MSW just right. Three days later, extracting the tissue juices, then diluting the tissue juices and coate on agar plates which have ciprofloxacin with a concentration of 0.5mg/L, so as to observe the growing condition of mutants. Results In vitro, against Acinetobacter baumannii, MIC, MPC and SI of ciprofloxacin were 0.5mg/L, 8.0mg/L and 16; and those of amikacin were 4.0mg/L, 64mg/L and 16,respectively. Single groups： mutants were found in 0.5, 1.0, 2.0 and 4.0mg/L groups, but none in 8.0mg/L group. It prompted that MPC of ciprofloxacin in vivo was the same to that in vitro, both 16. Combined groups： mutants were found in the group which concentration of ciprofloxacin was 0.5 and 1.0mg/L, while no mutants in the other groups. It showed MPC was 2.0mg/L and MIC was 0.25mg/L when ciprofloxacin combined amikacin, and SI became 8 in this condition. Conclusion Ciprofloxacin combined amikacin can reduce the mutant selective windows of ciprofloxacin against the Acinetobacter baumannii in rabbit and it will reduce the arising of mutants to control the resistance.