为揭示动物源大肠杆菌耐药性机制,追踪潜在的抗性基因传播机制及其来源,在先前公布的分离自鸡肠道的多抗耐药性菌株大肠杆菌Escherichia coli C20基因组基础上,对E.coli C20抗生素抗性基因种类、数量、来源及其耐药性机制进行分析.通过与已知的抗生素抗性基因数据库进行对比和注释,一共预测和注释了80个潜在的耐药性基因,包括与先前筛选的7种抗生素抗性对应的抗性基因.其中,喹诺酮类抗生素抗性基因位于C20基因组上,四环素、磺胺类、氯霉素、氨基糖苷类以及大环内酯类抗生素的抗性基因则位于C20环状质粒分子上.基因组聚类分析表明,菌株C20与大肠杆菌K-12菌株DH1、BW2952和MG1655亲缘关系较近,序列相似性97％～99％.3株K-12菌株基因组中没有发现与C20质粒类似的序列,表明C20菌株的抗性基因主要是通过质粒介导的水平基因转移方式从其他环境微生物中获得.%Spreading of antibiotic resistant bacteria in the environment has become a major concern for food safety and human health.Escherichia coli C20 was isolated from the gut microbiota of a domestic chicken that showed resistances to 7 out of 10 tested antibiotics.To elucidate the underlying mechanism,origin,and transmission of the resistances,published information on C20 genome were reviewed for a detailed analysis.There were 80 antibiotic resistance determinants,including the abovementioned 7 drugs,annotated in E.coli C20 genome from the databases.Among them,the fluoroquinolone-resistant genes were identified in the chromosomes,while those resistant to tetracycline,sulphonamide,chloramphenicol,and aminoglycoside found to be expressed in the plasmids of C20.A phylogenomic analysis on C20 revealed a clustering of the strain with E.coli K-12 group,especially the substrains of DH1,BW2952 and MG1655.Their genomic nucleoid sequences shared 97-99％ homology.There was no plasmid pC20-like sequence found in the genomic sequences of 3 K-12 strains reported previously.It was proposed that E.coli C20 isolated from the chicken guts might have acquired the antibiotic resistance through plasmid transfer from environmental microbiome.
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