He Tao, Shen Yingbo, Schwarz Stefan, Cai Jiachang, Lv Yuan, Li Jun, Feßler Andrea T, Zhang Rong, Wu Congming, Shen Jianzhong, Wang Yang
Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Veterinary Medicine, China Agricultural University, Beijing, China Institute of Food Safety & Detection, Jiangsu Academy of Agricultural Sciences, Nanjing, China.
Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Veterinary Medicine, China Agricultural University, Beijing, China.
J Antimicrob Chemother. 2016 Jun;71(6):1466-73. doi: 10.1093/jac/dkw016. Epub 2016 Feb 21.
Aim of this study was to analyse 17 non-related Enterococcus faecalis isolates of human and animal origin for the genetic environment of the novel oxazolidinone/phenicol resistance gene optrA.
WGS and de novo assembly were conducted to analyse the flanking sequences of the optrA gene in the 17 E. faecalis isolates. When optrA was located on a plasmid, conjugation assays were performed to check whether the plasmids are conjugative and to confirm the resistance phenotype associated with these plasmids.
All nine optrA-carrying plasmids were conjugated into E. faecalis JH2-2 and the transconjugants exhibited the optrA-associated phenotype. In these plasmids, an IS1216E element was detected either upstream and/or downstream of the optrA gene. In eight plasmids, the phenicol exporter gene fexA was found upstream of optrA and in six plasmids, a novel erm(A)-related gene for macrolide-lincosamide-streptogramin B resistance was detected downstream of optrA. When located in the chromosomal DNA, the optrA gene was found downstream of the transcriptional regulator gene araC in four isolates, or downstream of the fexA gene in another four isolates. Integration of the optrA region into a Tn558-Tn554 hybrid, located in the chromosomal radC gene, was seen in two isolates.
The findings of the present study extend the current knowledge about the genetic environment of optrA and suggest that IS1216E elements play an important role in the dissemination of optrA among different types of enterococcal plasmids. The mechanism underlying the integration of optrA into the chromosomal DNA requires further investigation.
本研究旨在分析17株来自人和动物的非相关粪肠球菌分离株中新型恶唑烷酮/甲砜霉素耐药基因optrA的遗传环境。
进行全基因组测序（WGS）和从头组装，以分析17株粪肠球菌分离株中optrA基因的侧翼序列。当optrA位于质粒上时，进行接合试验，以检查质粒是否可接合，并确认与这些质粒相关的耐药表型。
所有携带optrA的9个质粒都能接合到粪肠球菌JH2-2中，接合子表现出与optrA相关的表型。在这些质粒中，在optrA基因的上游和/或下游检测到一个IS1216E元件。在8个质粒中，甲砜霉素转运蛋白基因fexA位于optrA的上游，在6个质粒中，在optrA的下游检测到一个新的与大环内酯-林可酰胺-链阳菌素B耐药相关的erm(A)相关基因。当位于染色体DNA中时，在4株分离株中发现optrA基因位于转录调节基因araC的下游，在另外4株分离株中位于fexA基因的下游。在2株分离株中，观察到optrA区域整合到位于染色体radC基因中的Tn558-Tn554杂种中。
本研究结果扩展了目前关于optrA遗传环境的知识，并表明IS1216E元件在optrA在不同类型肠球菌质粒中的传播中起重要作用。optrA整合到染色体DNA中的潜在机制需要进一步研究。
