临床大肠埃希菌第Ⅰ类整合子检测及耐药基因盒分析

目的对来自临床腹泻患者大肠埃希菌的第Ⅰ类整合子分布及其耐药基因盒的结构特征进行分析。方法应用聚合酶链反应（PCR）方法检测第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序列分析。结果在40株大肠埃希菌中有28株（70％）第Ⅰ类整合酶基因阳性。耐药基因盒扩增结果，13株菌得到1664bp的扩增产物，10株得到1586bp的产物，3株得到1009bp的产物，2株得到1009bp和1586bp两种不同产物。序列分析结果表明，1664bp携带aadA5和dfr17，1586bp携带aadA1和dhfrⅠ，均为对氨基糖苷类抗生素壮观霉素、链霉素和磺胺类药物甲氧苄氨嘧啶产生耐药的基因盒；1009bp为aadA23b，为对氨基糖苷类抗生素壮观霉素、链霉素产生耐药的基因盒。结论测出的28株第Ⅰ类整合子阳性菌株携带耐氨基糖苷类抗生素的基因，应从基因水平上对细菌耐药及其传播进行监测。

Identification and characterization of class 1 integron-mediated antibiotic resistance among Escherichia coli clinical strains

Objective Since integrons play an important role in the spread of antibiotic resistance genes in bacteria,the distribution and characterization of the class 1 integron among E. coli strains from patients were investigated. Methods 40 clinical strains of E. coli were examined for their sensitivity to eight common antimicrobials. The presence and genetic content of class Ⅰ integron were examined with specific primers of int Ⅰ and genes cassettes by PCR and sequencing. Results Twenty-eight （70%）strains were positive for int Ⅰ gene. Furthermore,strains yield ing a PCR product of int Ⅱ gene were amplified by primers of in-F and in-B which were set for amplifying the region of antibiotics resistance genes. Among twenty-eight intⅠ-positive strains,an amplicon of 1 664 bp was yielded in 13 isolates; an amplicon of 1 586 bp was yielded in 10 isolates; an amplicon of 1009 bp was yielded in 3 isolates; 2 isolates presented two amplicons of 1 009 bp and 1 586 bp. Sequencing analysis revealed that amplicon 1 664 bp harbored gene cassette aadA5 and dfrlT, conferring resistant to spectinomycin-streptomycin and trimethoprim respectively. Another amplicon of 1 586 bp harbored gene aadA1 and dhfr I ,also conferring resistant to spectinomycin-strep- tomycin and trimethoprim. The amplicon of 1 009 bp harbored gene aadA23b,conferring resistant to spectinomycin and streptomycin. Conclusion Class 1 integron harboring multidrug resistance genes had been identified among E. coli clinical strains. The result stressed the need for continued surveillance of antibiotic resistance bacteria in the molecular level.