市售畜禽肉产CTX-M酶大肠杆菌的流行病学调查

Epidemiological investigation of CTX-M-producing Escherichia coli from retail livestock and chicken meat

摘要:

[目的] 调查市售畜禽肉类中大肠杆菌的耐药状况和bla_CTX-M基因的流行病学特征。[方法] 采集广州市不同区域零售市场和超市畜禽肉类样品进行大肠杆菌的分离，通过基因phoA扩增和测序进行大肠杆菌鉴定，采用琼脂扩散法和微量肉汤稀释法测定药物敏感性，通过PCR扩增检测bla_CTX-M基因，对bla_CTX-M阳性大肠杆菌进行全基因组测序。[结果] 从323份市售畜禽肉样品中分离获得大肠杆菌241株；药物敏感性结果表明大肠杆菌对氨苄西林（63.07%）、多西环素（47.72%）和复方新诺明（43.15%）耐药率较高；bla_CTX-M基因检出率为3.32%（n=8），其中4株携带bla_CTX-M-14，3株携带bla_CTX-M-65，1株携带bla_CTX-M-55；8株产CTX-M大肠杆菌可分为4种不同的ST型，且携带多种耐药基因和毒力基因。[结论] 市售畜禽肉中大肠杆菌污染严重。产CTX-M酶大肠杆菌均为多重耐药菌株，且bla_CTX-M基因主要以水平传播方式在大肠杆菌中传播，需要加强监测。

Abstract:

[Objective] To investigate antibiotic resistance and epidemiological characteristics of bla_CTX-M gene of Escherichia coli from retail livestock and chicken meat in Guangzhou. [Methods] E. coli was isolated from retail livestock and chicken meat samples in different regional retail markets and fresh supermarket in Guangzhou. Those isolates were identified by the gene phoA and sequencing. Drug susceptibility was determined by agar diffusion and broth microdilution method. The bla_CTX-M gene was detected using PCR amplification. Whole genome sequencing was performed in all bla_CTX-M-positive E. coli.[Results] A total of 241 strains were isolated from 323 meat samples. The drug susceptibility test shows that those strains were highly resistant to ampicillin (63.07%), doxycycline (47.72%) and sulfamethoxazole/trimethoprim (43.15%). The prevalence of bla_CTX-M gene was 3.32% (n=8), which contained 4 bla_CTX-M-14-positive strains, 3 bla_CTX-M-65-positive strains and 1 bla_CTX-M-55-positive strain. Eight CTX-M-producing E. coli were divided into four distinct ST types, which carried multiple resistance genes and virulence genes.[Conclusion] The contamination of E. coli was serious in retail meat. All CTX-M-producing E. coli were multi-resistant strains, and the dissemination of bla_CTX gene was mainly due to horizontal transfer, which needs further surveillance.