质粒 染色体介导的大肠埃希菌β-内酰胺酶基因型与耐药性分析

Genotype analysis of β-lactamases in escherichia coli and its relation to antibiotic resistance

目的研究产β-内酰胺酶大肠埃希菌基因型及其相关耐药性。方法对临床分离的7株大肠埃希菌,作β-内酰胺酶测定、药物敏感试验、质粒DNA转化和DNA印迹试验。结果7株大肠埃希菌,经E-test法检测,均产生超广谱β-内酰胺酶(ESBLs);质粒DNA电泳图谱显示7株大肠埃希菌均含有TEM型耐药质粒;通过大肠埃希菌质粒DNA和染色体DNA印迹试验证明7株大肠埃希菌耐药由质粒介导或由质粒与染色体共同介导。结论第一株大肠埃希菌β-内酰胺酶单纯由质粒介导,第2～7株大肠埃希菌β-内酰胺酶由质粒和染色体共同介导。由质粒与染色体双重介导的β-内酰胺酶增强了大肠埃希菌对抗生素的耐药性。

Objective To study antibiotic sensitivities and characterization of β-1actamase activity. To characterize the isolates with respect to their antibiotic resistance mechanisms. Methods To characterize β-lactamases, agar dilution method was used to determine the minimum inhibitory concentration （MIC） of antibiotics. The plasmids of clinical isolates were cloned into competent cells. Southern analysis was carried out with the clinical strains to identify the number of TEM β-laetamases present. Analysis was carried out on both plasmid and genomic DNA to identify the location of these genes. Results All seven isolates are expressing TEM enzyme. The last five isolates are expressing AmpC with the last two isolates hyper-produeing this enzyme. Conclusion The increases in expression of AmpC from the chromosomal locus in the five clinical strains are due to mutations in the promoter and attenuator.