致病性大肠埃希菌对头孢噻呋的耐药性研究

目的]以头孢噻呋为底物将大肠埃希菌标准菌株诱导为耐药菌株,研究诱导的耐药菌株对头孢噻呋产生耐药性的机制。方法]用亚抑菌浓度法对标准菌株C83907和C83845进行诱导,诱导10代后用双纸片法和PCR扩增法,进行超广谱β-内酰胺酶（Extendspectrumβ-lactamses,ESBLs）检测;用试管2倍稀释法测定头孢噻呋对产ESBLs菌株的最小抑菌浓度值;对产生ESBLs的耐药菌株,用试管2倍稀释法测定了头孢噻呋与他唑巴坦钠以不同配比对产生ESBLs大肠埃希菌的最小抑菌浓度。结果]诱导15代后,头孢噻呋对诱导菌的MIC值8～10μg/ml,且均检测出ESBLs;头孢噻呋与他唑巴坦钠质量比（1∶1～8∶1）联合使用对产生ESBLs的大肠埃希菌的最小抑菌浓度较头孢噻呋单独使用降低20～22倍。结论]致病性大肠埃希菌对头孢噻呋产生耐药性的主要机制是产生了ESBLs。

Study on the Resistance of Pathogenic Escherichia coli to Ceftiofur

Objective] Ceftiofur was as the substrate to induce the standard strain of Escherichia coli(E.coli)to be the drug-resistance one.The resistant mechanism of E.coli to ceftiofur was studied.Method] The sub-inhibitory concentration method was used to induce the standard strains C83907 and C83845.After they were induced for 10 generations,the double disc synergy test(DDST),NCCLS(National Committee for Clinical Laboratory Standards)confirmatory test and PCR amplification were used to detect the extend spectrum β-lactamases(ESBLs).The two fold dilution method was used to measure the minimal inhibitory concentration(MIC)of cetiofur to the strain which produced ESBLs.For the drug-resistance strain which produced ESBLs,the two fold dilution method was used to measure the minimal inhibitory concentrations of different proportions of cetiofur and tazobactam sodium.Result] After they were induced 15 generations,MIC value of ceftiofur to the induced bacteria was during 8-10 μg/ml,and ESBLs was detected.MICs of cetiofur combining tazobactam sodium(the mass ratio was 1∶1-8∶1)to Escherichia coli produced ESBLs reduced 20-22 times than that of cetiofur.Conclusion] The main mechanism of pathogenic Escherichia coli resistance to ceftiofur was that which produced ESBLs.