猪链球菌中的一个噬菌体和两个携带 optrA 的 ICESa2603 家族整合性和可转移性遗传元件 (ICEs)。
A prophage and two ICESa2603-family integrative and conjugative elements (ICEs) carrying optrA in Streptococcus suis.
机构信息
College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, P. R. China.
Institute of Microbiology and Epizootics, Centre for Infection Medicine, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany.
出版信息
J Antimicrob Chemother. 2019 Oct 1;74(10):2876-2879. doi: 10.1093/jac/dkz309.
OBJECTIVES
To investigate the presence and transfer of the oxazolidinone/phenicol resistance gene optrA and identify the genetic elements involved in the horizontal transfer of the optrA gene in Streptococcus suis.
METHODS
A total of 237 S. suis isolates were screened for the presence of the optrA gene by PCR. Whole-genome DNA of three optrA-positive strains was completely sequenced using the Illumina MiSeq and Pacbio RSII platforms. MICs were determined by broth microdilution. Transferability of the optrA gene in S. suis was investigated by conjugation. The presence of circular intermediates was examined by inverse PCR.
RESULTS
The optrA gene was present in 11.8% (28/237) of the S. suis strains. In three strains, the optrA gene was flanked by two copies of IS1216 elements in the same orientation, located either on a prophage or on ICESa2603-family integrative and conjugative elements (ICEs), including one tandem ICE. In one isolate, the optrA-carrying ICE transferred with a frequency of 2.1 × 10-8. After the transfer, the transconjugant displayed elevated MICs of the respective antimicrobial agents. Inverse PCRs revealed that circular intermediates of different sizes were formed in the three optrA-carrying strains, containing one copy of the IS1216E element and the optrA gene alone or in combination with other resistance genes.
CONCLUSIONS
A prophage and two ICESa2603-family ICEs (including one tandem ICE) associated with the optrA gene were identified in S. suis. The association of the optrA gene with the IS1216E elements and its location on either a prophage or ICEs will aid its horizontal transfer.
目的
研究恶唑烷酮/氯霉素耐药基因 optrA 的存在和转移，并鉴定与屎肠球菌 optrA 基因水平转移相关的遗传元件。
方法
通过 PCR 筛选 237 株屎肠球菌，检测 optrA 基因的存在。采用 Illumina MiSeq 和 Pacbio RSII 平台对 3 株 optrA 阳性株的全基因组 DNA 进行完全测序。采用肉汤微量稀释法测定 MIC。通过接合试验研究 optrA 基因在屎肠球菌中的可转移性。通过反向 PCR 检测环形中间体的存在。
结果
237 株屎肠球菌中有 11.8%（28/237）携带 optrA 基因。在 3 株菌中，optrA 基因两侧为两个同向的 IS1216 元件，位于噬菌体或 ICEs（包括一个串联 ICE）上。在一个分离株中，携带 optrA 的 ICE 转移频率为 2.1×10-8。转移后，转导子对相应抗菌药物的 MIC 值升高。反向 PCR 显示，在 3 株携带 optrA 的菌株中形成了不同大小的环形中间体，其中含有一个 IS1216E 元件和单独的 optrA 基因，或与其他耐药基因组合。
结论
在屎肠球菌中发现了与 optrA 基因相关的一个噬菌体和两个 ICESa2603 家族 ICEs（包括一个串联 ICE）。optrA 基因与 IS1216E 元件的关联及其位于噬菌体或 ICEs 上的位置将有助于其水平转移。
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