四川省食品动物源大肠杆菌mcr-1与ESBLs基因共转移分析

Analysis of co-transfer of mcr-1 and ESBLs genes in Escherichia coli isolates from food-producing animals in Sichuan Province

为了解四川省食品动物源大肠杆菌mcr-1耐药基因流行情况,及其与超广谱β-内酰胺酶基因(ESBLs)共存和共转移的特征,采用微量肉汤稀释法检测菌株对不同抗菌药物的敏感性;采用PCR检测菌株mcr-1,以及mcr-1阳性菌株中ESBLs基因类型;采用质粒接合转移试验分析了mcr-1与ESBLs基因共转移的耐药机制。结果显示:190株大肠杆菌的mcr-1检出率为36.84%,75.71%mcr-1阳性菌株中同时检出ESBLs基因,主要以blaTEM-1、blaCTX-M-55和blaCTX-M-14为优势基因;mcr-1阳性菌对氨曲南(ATM)、头孢噻肟(CTX)和多黏菌素E(COL)耐药率极显著高于mcr-1阴性菌(P<0.01);质粒转移率为47.14%,其中获得mcr-1和ESBLs基因共转移的接合子表现出与供体菌相同的耐药表型及耐药基因。综上,在四川省食品动物源大肠杆菌中,mcr-1与ESBLs基因共存现象广泛存在,且耐药基因易发生水平传播,对菌株多重耐药性的产生具有重要意义。

The aim of this study was to investigate the prevalence of mcr-1 and the co-tansfer of mcr-1 with ESBLs genes in Escherichia coli from food-producing animals in Sichuan Province.The sensitivity of mcr-1 to different antibiotics was detected by broth microdilution method;The ESBLs gene type of mcr-1 positive strains were detected by PCR;The drug resistance mechanism of co-transfer of mcr-1 and ESBLs gene was analyzed by plasmid conjugation transfer test.The results showed that:The detection rate of mcr-1 in 190 E.coli isolates was 36.84%,and 75.71%mcr-1 positive strains was detected ESBLs gene simultaneously,mainly blaTEM-1,blaCTX-M-55 and blaCTX-M-14 as the dominant genes;The resistant rate of mcr-1 positive strains to aztreonam,cefotaxime and colistin was very significantly higher than that of negative strains(P<0.01);The rate of plasmid conjugation was 47.14%.The transconjugants with mcr-1 and ESBLs of co-transfer had acquired resistant phenotype and genotypes from parental strains.In conclusion,in the food-producing animals source of E.coli in Sichuan Province,the coexistence of mcr-1 and ESBLs genes is widespread and the resistant genes is easy to spread horizontally,which is of great significance to the production of multiple drug resistance of strains.