An integron cassette carrying dfr1 with 90-bp repeat sequences located on the chromosome of trimethoprim-resistant isolates of Campylobacter jejuni
An integron cassette carrying dfr1 with 90-bp repeat sequences located on the chromosome of trimethoprim-resistant isolates of Campylobacter jejuni
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DOI：
10.1089/107662900419384
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发表时间：
2000-06-01
影响因子：
2.6
通讯作者：
Sköld, O
中科院分区：
文献类型：
--
作者：
Gibreel, A;Sköld, O
空肠弯曲菌临床分离株对甲氧普林高度耐药的频繁发生与获得编码二氢叶酸还原酶耐药变异的外来耐药基因(dfr1或dfr9或两者)有关，二氢叶酸还原酶是甲氧嘧啶的靶标。对40株空肠弯曲菌临床分离株染色体上的dfr1基因的结构和遗传组织进行了进一步研究。大多数dfr1基因以整合子盒的形式插入到染色体中。在36%的受检分离株中，dfr1基因与以前在耐甲氧普林的大肠杆菌中的特征相同，在40%的病例中，检测到含有90bp直接重复序列的dfr1基因的变异体，在5%的分离物中，发现含有重复序列的dfr1变异体在整合子环境中以两盒串联的形式出现。研究发现，dfr1基因编码序列中90bp重复序列的存在在空肠弯曲菌对甲氧苄氨嘧啶环境浓度的适应中发挥了作用。
The frequent occurrence of high-level trimethoprim resistance in clinical isolates of Campylobacter jejuni was shown to be related to the acquisition of foreign resistance genes (dfr1 or dfr9 or both) coding for resistant variants of the enzyme dihydrofolate reductase, the target of trimethoprim. The dfr1 gene detected on the chromosome of 40 different clinical strains of C. jejuni was studied further regarding structure and genetic organization. Most of the dfr1 genes were found as integron cassettes inserted in the chromosome. In 36% of the examined isolated, the dfr1 gene showed identity to that previously characterized in trimethoprim-resistant Escherichia coli, In 40% of the cases, however, a variant of the dfr1 gene containing a 90-bp direct repeat was detected, and in 5% of the isolates, the repeat-containing dfr1 variant was found to occur in the form of two cassettes in tandem in an integron context. The existence of the 90-bp repeat within the coding sequence of the dfr1 gene was found to play a role in the adaptation of C. jejuni to ambient concentrations of trimethoprim.