食品中大肠埃希菌耐药性与整合子的关系研究

目的研究食品中大肠埃希菌的整合子携带情况及其与耐药性之间的关系。方法PCR检测细菌总DNA中1、2、3类整合酶基因，确定细菌携带整合子的情况。阳性菌株进一步检测整合子的可变区，分析插入基因盒的序列。结果50株大肠埃希菌中19株携带1类整合子，2株携带2类整合子，集中分布在对4种以上抗生素耐药的菌株中。插入基因盒主要是dfr和aadA类基因盒，各种基因盒组合中最常见的是dfr17-aadA5。结论细菌的多重耐药性与整合子携带高度一致，但是单个菌株的耐药谱与整合子的耐药基因盒缺乏对应关系。

Relationship between Antibiotic Resistance and Integrons of Escherichia coli Isolated from Food

Objective To investigate the relationship between antibiotic resistance of Escherichia coli strains isolated from food and the integrons they harbored. Methods PCRs amplifying intI gene and the variable region between the conserved segments (CS-PCR) were performed for class1, class2, and class 3 integron. And the integron content of every isolate was characterized by RFLP analysis and sequencing. Results 19 of 50 isolates were identified as being positive for integrase 1 gene in the genomic DNA, of which 13 had detectable amplification products for CS-PCR. Two E.coli isolates had class 2 integron. All the integron-positive strains were resistance to at least 4 antibiotics. Most of the gene cassettes integrated in the integrons conferred resistance against trimethoprim and streptomycin-spectinomycin, and the integrons with the dfr17-aadA5 gene cassettes combination were predominant. Some strains with different antibiotic resistance profile or plasmid profile were found to have the same integron. Conclusion There was a good correlation between Integron-carrying and the antibiotic resistance of Escherichia coli strains isolated from food, but in terms of an individual strain, its antibiotic profile was not consistent with the gene cassettes of the integron it harbored.