A novel cfr-carrying Tn7 transposon derivative characterized in Morganella morganii of swine origin in China
A novel cfr-carrying Tn7 transposon derivative characterized in Morganella morganii of swine origin in China
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DOI：
10.1093/jac/dky494
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发表时间：
2019-03-01
影响因子：
5.2
通讯作者：
Wang, Hongning
中科院分区：
文献类型：
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作者：
Chen, Yanpeng;Lei, Changwei;Wang, Hongning
目的了解猪场细菌分离株中多药耐药基因cfr的存在及其遗传环境。方法对某猪场采集的32份粪便标本中分离到的97株细菌，用聚合酶链式反应(PCR)检测cfr基因的存在情况。使用BD Phoenix(TM)100自动微生物系统对一株CFR阳性菌株进行了物种鉴定。药敏试验采用微量肉汤稀释法。结果摩根摩根菌BCMM24是唯一一株CFR阳性菌株。CFR基因和其他15个抗性基因位于Tn6451转座子上，该转座子由多种遗传物质组成，包括一个新的带有5个基因盒的1类整合子。该基因由一个新的遗传结构IS26-CFR-Tn554TnpB-TnpB-TnpA-IS26组成，不同于以往的报道。两步聚合酶链式反应的结果表明，Tn6451的结构可以被环化，而Tn6451不能从染色体上被切除。CFR基因和其他15个耐药基因位于一个新的Tn7转座子衍生物上，这表明Tn7转座子可能是各种耐药基因的储存库，在动物和人类来源的革兰氏阴性菌中可能发现更多携带多个耐药基因的Tn7衍生物。
Objectives To characterize the presence and genetic environment of the multiresistance gene cfr in bacterial isolates from a swine farm.Methods A total of 97 bacterial isolates, recovered from 32 faecal swabs obtained on one farm, were tested for the presence of the cfr gene by PCR. Species identification of the one cfr-positive strain was conducted using the BD Phoenix(TM) 100 Automated Microbiology System. Susceptibility testing was carried out by broth microdilution. The genetic environment of the cfr gene was analysed by WGS.Results The Morganella morganii isolate BCMM24 was the only cfr-positive strain. The cfr gene, as well as 15 other resistance genes, is located on a novel 111238bp transposon derived from Tn7, designated as Tn6451, which comprises various genetic materials including a novel class 1 integron with five gene cassettes. The cfr-containing region consists of a novel genetic structure IS26-cfr-Tn554 tnpB-Tn3 family tnpA-IS26, differing from previous reports. Two-step PCR results show that the structure can be looped out and that Tn6451 cannot be excised from the chromosome.Conclusions To the best of our knowledge, we report the cfr gene in M. morganii for the first time. The cfr gene and 15 other resistance genes are located on a novel Tn7 transposon derivative, suggesting that the Tn7 transposon may act as a reservoir for various antimicrobial resistance genes and more Tn7 derivatives carrying multiple resistance genes are likely to be discovered in Gram-negative bacteria of both animal and human origin.