CHU de Rennes, Service de Bactériologie-Hygiène hospitalière, Rennes, France.
Université de Rennes 1, Inserm U1230, Rennes, France.
J Antimicrob Chemother. 2021 Jul 15;76(8):1978-1985. doi: 10.1093/jac/dkab116.
To describe the prevalence of poxtA among clinical linezolid-resistant enterococci (LRE) collected in France from 2016 to 2020 and to extensively characterize its genetic supports and environments.
All LRE clinical isolates received at the National Reference Centre for Enterococci from French hospitals between 2016 and 2020 were included. LRE isolates were screened for linezolid resistance genes (cfr-like, optrA and poxtA) by real-time PCR and phenotypically characterized. A collection of 11 representative poxtA-positive isolates (10 Enterococcus faecium and 1 Enterococcus faecalis) underwent WGS by hybrid assembly combining short-read (Illumina MiSeq) and long-read (MinION) approaches. Transferability of poxtA was attempted by filter-mating experiments.
Out of 466 LRE received at the National Reference Centre for Enterococci over the period, 47 (10.1%) were poxtA-positive, including 42 E. faecium. The 11 isolates characterized by WGS were confirmed to be epidemiologically unrelated by core genome analysis and eight different STs were assigned to E. faecium isolates. The poxtA gene was found to be plasmid carried and flanked by IS1216E transposase genes in all isolates and frequently linked with fexB, tet(M) and tet(L). A total of seven distinct poxtA-harbouring plasmids were obtained after hybrid assembly and plasmid transfer of poxtA was successful in three cases. For the two poxtA/optrA-positive isolates, those genes were carried by different plasmids.
The poxtA gene has been circulating among clinical enterococci in France since at least 2016, mostly in E. faecium and independently from optrA. The poxtA-carrying plasmids often co-carried resistance genes to phenicols and tetracyclines, and could have been co-selected through their veterinary use.
描述 2016 年至 2020 年期间在法国收集的临床利奈唑胺耐药肠球菌（LRE）中 poxtA 的流行情况，并对其遗传支持和环境进行广泛表征。
纳入 2016 年至 2020 年期间法国各医院向国家肠球菌参考中心送检的所有 LRE 临床分离株。通过实时 PCR 筛选利奈唑胺耐药基因（cfr-like、optrA 和 poxtA）并进行表型特征分析。对 11 株 poxtA 阳性代表性分离株（10 株屎肠球菌和 1 株粪肠球菌）进行 WGS 分析，采用短读（Illumina MiSeq）和长读（MinION）混合组装的杂交组装方法。通过滤膜交配实验尝试转移 poxtA。
在该研究期间，国家肠球菌参考中心共收到 466 株 LRE，其中 47 株（10.1%）为 poxtA 阳性，包括 42 株屎肠球菌。通过 WGS 鉴定的 11 株分离株通过核心基因组分析证实为流行病学上无关，共鉴定出 8 种不同的 ST 型，这些 ST 型与屎肠球菌分离株相关。poxtA 基因在所有分离株中均发现位于质粒上，两侧为 IS1216E 转座酶基因，并且经常与 fexB、tet(M) 和 tet(L) 相连。通过混合组装获得了 7 种不同的 poxtA 携带质粒，在 3 种情况下成功进行了 poxtA 的质粒转移。对于 2 株 poxtA/optrA 阳性分离株，这两种基因位于不同的质粒上。
自 2016 年以来，poxtA 基因一直在法国临床肠球菌中传播，主要存在于屎肠球菌中，与 optrA 无关。携带 poxtA 的质粒通常还携带对青霉素和四环素的耐药基因，并且可能通过其在兽医中的使用而被共同选择。
