畜禽源大肠杆菌质粒介导β-内酰胺酶检测及其耐药基因特性研究

Detection of Escherichiacoliplasmid-mediatedβ-lactamase from livestock and poultry and characterization of antimicrobial resistance

为探讨畜禽源大肠杆菌临床菌株产β-内酰胺酶及其基因特性,采用常规检测法检测菌株产β-内酰胺酶情况,PCR法检测ESBLs、AmpC基因型,质粒结合转移试验研究耐药基因分子传播机制,并使用微量肉汤稀释法检测供体菌及接合子的药物敏感性。结果显示:467株食品动物源大肠杆菌未检出产碳青霉烯酶和金属β-内酰胺酶,产ESBLs和AmpC分别达36.83%和13.70%;176株产β-内酰胺酶菌株检出blaTEM、blaCTX-M、blaOXA、blaCIT和blaDHA分别为84.09%、60.80%、14.77%、35.80%和1.70%;本次质粒转移率为50%,多数转化子获得了供体菌的耐药性及耐药基因。以上结果说明,产ESBLs、AmpC菌株广泛存在于本次检测菌株中,blaTEM、blaCTX-M和blaCIT是β-内酰胺酶基因主要流行基因型,质粒在β-内酰胺酶基因的水平传播起主要作用。

To detect and characterize plasmid-mediatedβ-lactamase in E.coli isolates derived from livestock and poultry,the prevalence ofβ-lactamase in E.coli isolates was investigated by conventional test.Genotypes of extended spectrumβ-lactamases（ESBLs）and AmpC were detected by PCR;Genetic transmission ofβ-lactamase genes was carried by plasmid conjugation experiment;Antimicrobial susceptibility of donors and transconjugants was tested by using broth micro dilution method.The results showed that the detection rates of carbapenemase,metallo-β-lactamase,ESBLs and AmpC in 467 E.coli isolates were 0.00%,0.00%,36.83% and 13.70%,respectively;The prevalence rates of blaTEM,blaCTX-M,blaOXA,blaCIT and blaDHA in 176β-lactamase positive strains were 84.09%,60.80%,14.77%,35.80% and 1.70%,respectively;The positive rate of plasmid conjugation was 50.00%in the study,and the majority of transconjugants had acquired antimicrobial resistance phenotypes and genotypes originated from parental isolates.In conclusion,ESBLs or/and AmpC producing strains exist widely among the isolates tested,blaTEM,blaCTXM and blaCIT are dominant genetypes,and horizontal plasmid transfer plays a major role in the spread ofβ-lactamase genes in E.coli.