动物源大肠埃希氏菌QnrS阳性株体内氟喹诺酮药物蓄积的研究

【目的】研究氟喹诺酮类药物在动物源大肠埃希氏菌QnrS阳性株体内蓄积量的变化规律,探讨主动外排机制在携QnrS菌株中的作用。【方法】采用肉汤微量稀释法测定QnrS阳性株对氟喹诺酮类药物的MIC,荧光测定法检测盐酸环丙沙星在QnrS阳性株体内浓度的变化及能量抑制剂碳酰氰间氯苯腙(CCCP)对菌体内药物蓄积的影响。【结果】动物源大肠埃希氏菌QnrS阳性株对氟喹诺酮药物的敏感性存在明显差异,均对盐酸环丙沙星的蓄积呈能量依赖性降低,其中以耐药株体内的药物浓度降低最为明显。加入能量抑制剂后,耐药株体内的药物浓度上升程度明显高于敏感株,但均达不到标准株体内药物浓度水平。【结论】主动外排泵的激活,使受试菌体内盐酸环丙沙星减少并低于有效浓度,从而影响QnrS介导的氟喹诺酮类耐药性。

Study on the Accumulation of Fluoroquinolones in QnrS-Positive Animal Clinical Isolates of Escherichia coli

Objective] The objective of the experiment was to determine the susceptibility of fluoroquinolones and the effect of active efflux pump in QnrS-positive animal clinical isolates of E. coli. Method] The broth dilution method was used to determine MICs of fluoroquinolones against the QnrS-positive isolates. The accumulation of ciprofloxacin and the effect of efflux pump inhibitor,carbonyl cyanide m-chlorophenyl hydrazone (CCCP) for tested isolates of E. coli were measured by a fluorescenece method. Result] The susceptibility of QnrS-positive animal clinical isolates of E. coli to fluoroquinolone antibiotics varied greatly and decreased with energy dependence. The decrease in resistant isolates with QnrS was prominent. CCCP could increase the accumulation of ciprofloxacin in both the susceptible and the resistant strains of QnrS-positive isolates.However,the decrease of the latter was lower than the former. Conclusion] The accumulation of ciprofloxacin in QnrS-posidve animal clinical isolates of E. coli could be reduced and lower than the effective concentration by activating of active efflux pump,which affected the plasmid-mediated resistance.