Analysis of two pheromone-responsive conjugative multiresistance plasmids carrying the novel mobile optrA locus from Enterococcus faecalis
Analysis of two pheromone-responsive conjugative multiresistance plasmids carrying the novel mobile optrA locus from Enterococcus faecalis
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DOI：
10.2147/idr.s206295
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发表时间：
2019-01-01
影响因子：
3.9
通讯作者：
Du, Xiang-Dang
中科院分区：
文献类型：
--
作者：
Shang, Yanhong;Li, Dexi;Du, Xiang-Dang
背景资料：获得性optrA基因编码ABC-F家族的核糖体保护蛋白，可赋予对利奈唑胺和氟苯尼考的交叉耐药性，对人类和兽医学提出了严重的治疗挑战。方法：对两种质粒进行全序列测定和序列分析，以阐明它们的精细结构、可转移性和移动的耐药位点。除接合实验外，还进行了反向PCR实验，以观察微环是否从移动的抗菌素抗性位点产生。pE 211和pE 508的转移频率分别为2.6 × 10 ~（-2）和3.7 × 10 ~（-2）（每个供体的转移接合子）。在这两个质粒中，optrA位于新的移动的optrA基因座上，具有不同的大小（pE 211中分别为12，834 bp，pE 508中分别为7，561 bp），两侧是两个相同方向的IS 1216基因拷贝。反向PCR显示可以产生环状形式，由optrA和IS 1216的一个拷贝组成，表明它们都是活性的。77，562 bp质粒pE 211也携带Tn 558和一个移动的bcrABDR位点，84，468 bp质粒pE 508也携带fexA、泰特（L）、泰特（O/W/32/O）和移动的aac（A）-aph（D）基因座。在这些质粒中存在移动的遗传元件使它们具有柔性，并且这些元件将有助于这些质粒的持久性和传播肠球菌和其他革兰氏阳性菌中。
Background: The acquired optrA gene, which encodes a ribosomal protection protein of the ABC-F family, can confer cross-resistance to linezolid and florfenicol, posing a serious therapeutic challenge to both human and veterinary medicine.Purpose: The objective of this study was to investigate the two Enterococcus faecalis (E. faecalis) plasmids for their fine structure, their transferability and the presence of mobile antimicrobial resistance loci.Methods: To elucidate their fine structure, the two plasmids were completely sequenced and the sequences analysed. Besides conjugation experiments, inverse PCR assays were conducted to see whether minicircles are produced from the mobile antimicrobial resistance loci.Results: Two pheromone-responsive conjugative optrA-carrying plasmids from E. faecalis, pE211 and pE508 were identified, which can transfer with frequencies of 2.6 x10(-2) and 3.7 x10(-2) (transconjugant per donor), respectively. In both plasmids, optrA was located on the novel mobile optrA locus with different sizes (12,834 bp in pE211 and 7,561 bp in pE508, respectively), flanked by two copies of IS1216 genes in the same orientation. Inverse PCR revealed that circular forms can be generated, consisting of optrA and one copy of IS1216, indicating they are all active. The 77,562 bp plasmid pE211 also carried Tn558 and a mobile bcrABDR locus, and the 84,468 bp plasmid pE508 also harbored the genes fexA, tet(L), tet (O/W/32/O) and a mobile aac(A)-aph(D) locus.Conclusion: The presence of mobile genetic elements in these plasmids renders them flexible and these elements will aid to the persistence and dissemination of these plasmids among enterococci and potentially also other gram-positive bacteria.