大肠埃希菌中新的耐药基因盒aadA23的变异

目的基于整合子-细菌耐药系统在细菌耐药机制中的重要作用,对成人腹泻患者的大肠埃希菌Ⅰ类整合子阳性菌株携带的耐药基因盒的基因特征进行分析.方法应用聚合酶链反应（PCR）检测Ⅰ类整合酶基因intⅠ阳性菌株并对其整合的耐药基因进行测序及用生物信息软件对序列进行分析.结果5株Ⅰ类整合酶基因阳性菌株的耐药基因盒PCR扩增得到1009 bp的产物.序列分析结果表明,1009 bp序列含有780 bp的开放阅读框,与已知的aadA23和aadA21分别有99.6%和99.5%的相似性,与aadA5只有66.4%相似,为对氨基糖苷类抗菌药物壮观霉素、链霉素产生耐药的基因盒,建议命名为aadA23b.结论随着选择环境不同,整合子整合的基因盒会发生变异,提示我们要用分子生物学的手段从基因水平分析耐药基因的遗传与变异.

Detection of a new gene cassette aadA23 in Escherichia coli

Objective Since integrons play an important role in the spread of antibiotic resistance genes in bacteria, the characterization of a new resistance gene cassette in class 1 integron positive strains of E. coli was analyzed. Methods The presence and genetic content of class 1 integron were examined by PCR and sequencing. The sequence was analyzed by using some bioinformatics softwares. Results 5 class 1 integron positive strains were amplified by primers of in-F and in-B which were set for amplifying the region of antibiotics resistance genes. Among the 5 strains, an amplicon of 1009 bp was yielded. Sequencing analysis revealed that amplicon of 1009 bp harbored a 780 bp ORF. Further analysis with bioinformatics software showed that it was 99.6% and 99.5% identical to the known aadA23 and aadA21 cassette, and was just 66.4% identical to the known aadA5 cassette. It was conferring resistant to spectinomycin and streptomycin, and was given a new name aadA23b. Conclusions Multi-drug resistance genes has been proved changeable in E. coli clinical strains. The result not only stressed the need for continuing surveillance of antibiotic resistance in the molecular level, but also the need caring for genetic variation of drug resistance gene cassettes.