Yu Hak Sun, Lee Je Chul, Kang Hee Young, Jeong Young Sook, Lee Eun Young, Choi Chul Hee, Tae Seong Ho, Lee Yoo Chul, Seol Sung Yong, Cho Dong Taek
Department of Microbiology, School of Medicine, Kyungpook National University, 101, Dongin-dong, Jung-gu, Daegu, 700-422, Korea.
J Antimicrob Chemother. 2004 Mar;53(3):445-50. doi: 10.1093/jac/dkh097. Epub 2004 Feb 12.
The association of trimethoprim-resistant dfr genes with integrons was investigated in urinary Escherichia coli isolates in Korea from the last two decades.
Of 623 E. coli isolates from urine specimens, 421 trimethoprim-resistant isolates were studied for dfr genes associated with integrons. Integrase genes were amplified and the PCR products restricted using HinfI to classify integron types. Gene cassette regions for the class 1 and class 2 integrons were amplified and sequenced. PFGE was performed to determine the epidemiological relationship of E. coli isolates.
The carriage of class 1 integrons was found to be significantly higher in trimethoprim-resistant isolates (69%) than in trimethoprim-susceptible isolates (19%). Among the trimethoprim-resistant isolates, the frequency of dfr genes associated with class 1 integrons increased sharply from 10% of the isolates during 1980-1985 to 53% during 1996-1997 and to 46% during 2001-2002. Five different dfr cassettes--dfrA1, dfrA5, dfrA7, dfrA12 and dfrA17--were identified among the urinary E. coli isolates from the last two decades; dfrA12 was the most prevalent during 1980-1985 and dfrA17 during 1996-1997 and 2001-2002. The majority of dfr genes associated with class 1 integrons were conjugally transferable to recipient E. coli strains. The E. coli isolates that carried dfrA17 associated with class 1 integrons were found to be phylogenetically unrelated, indicating that dfrA17 was widely distributed in the different clones of E. coli.
Class 1 integrons were found to be an important genetic element of resistance to trimethoprim among urinary E. coli in Korea, and the prevalence of dfrA17 was mainly due to the horizontal transfer of class 1 integrons through conjugative plasmids.
对过去二十年韩国尿源大肠杆菌分离株中耐甲氧苄啶的dfr基因与整合子的关联进行研究。
在623株尿标本分离的大肠杆菌中,对421株耐甲氧苄啶分离株进行与整合子相关的dfr基因研究。扩增整合酶基因,并用HinfI对PCR产物进行酶切以分类整合子类型。对1类和2类整合子的基因盒区域进行扩增和测序。进行脉冲场凝胶电泳(PFGE)以确定大肠杆菌分离株的流行病学关系。
耐甲氧苄啶分离株中1类整合子的携带率(69%)显著高于甲氧苄啶敏感分离株(19%)。在耐甲氧苄啶分离株中,与1类整合子相关的dfr基因频率从1980 - 1985年分离株的10%急剧增加到1996 - 1997年的53%以及2001 - 2002年的46%。在过去二十年的尿源大肠杆菌分离株中鉴定出五种不同的dfr基因盒——dfrA1、dfrA5、dfrA7、dfrA12和dfrA17;dfrA12在1980 - 1985年最为普遍,dfrA17在1996 - 1997年和2001 - 2002年最为普遍。大多数与1类整合子相关的dfr基因可通过接合转移至受体大肠杆菌菌株。发现携带与1类整合子相关的dfrA17的大肠杆菌分离株在系统发育上不相关,表明dfrA17广泛分布于大肠杆菌的不同克隆中。
1类整合子是韩国尿源大肠杆菌中耐甲氧苄啶的重要遗传元件,dfrA17的流行主要归因于1类整合子通过接合性质粒的水平转移。