中国临床药理学杂志

目的 对比分析鸟肠球菌中线性质粒的分子特征，明确肠球菌线性质粒的全球传播轨迹，并通过接合子传代培养，探究不同宿主菌株中线性质粒的遗传稳定性，为临床耐药菌防控提供理论依据。方法 采用微量肉汤稀释法测定鸟肠球菌ZB195、3株受体菌(鸟肠球菌07H170、粪肠球菌FA2-2、屎肠球菌BM4105RF)及其对应接合子的万古霉素最低抑菌浓度(MIC);对ZB195菌株进行全基因组测序，解析其质粒特征;收集2000～2019年全球18株屎肠球菌的线性质粒序列，通过MAFFT、IQtree及BEAST软件构建系统发育树与贝叶斯进化树，结合Sprea D3软件模拟全球传播轨迹;通过15 d无抗菌药选择压力的传代试验，评估线性质粒在不同宿主中的遗传稳定性。结果 本研究首次于鸟肠球菌ZB195基因组中发现线性质粒，该质粒含万古霉素耐药基因van A，可水平转移至3株受体菌。序列比对显示，ZB195线性质粒与日本屎肠球菌AA708线性质粒序列一致度最高，系统发育分析证实二者亲缘关系最近。全球传播轨迹模拟显示，肠球菌线性质粒最早于2000年在日本检出，随后逐步扩散至中国、美国、挪威、丹麦及印度等国家。传代试验表明，线性质粒在鸟肠球菌宿主中稳定性最优。结论 中国肠球菌检出的线性质粒可能起源于日本屎肠球菌的水平传播，且该质粒转移至鸟肠球菌后可形成更优的宿主适应性，提示需加强肠球菌线性质粒的跨区域监测，以遏制耐药基因的全球扩散。

Objective To comparatively analyze the molecular characteristics of linear plasmids in Enterococcus avium,clarify the global transmission trajectory of linear plasmids in Enterococcus,and explore the genetic stability of linear plasmids in different host strains through subculture of transconjugants,thereby providing a theoretical basis for the prevention and control of clinically drug-resistant bacteria. Methods The minimum inhibitory concentrations( MICs) of vancomycin against Enterococcus avium ZB195,three recipient strains( Enterococcus avium07H170, Enterococcus faecalis FA2-2, and Enterococcus faecium BM4105 RF),and their corresponding transconjugants were determined using the broth microdilution method. Whole-genome sequencing of strain ZB195 was performed to characterize its plasmid features. Linear plasmid sequences from 18 global Enterococcus faecium strains isolated between 2000 and 2019 were collected, and phylogenetic trees and Bayesian evolutionary trees were constructed using MAFFT,IQtree,and BEAST software. The global transmission trajectory was simulated with SpreaD3 software. The genetic stability of linear plasmids in different host strains was evaluated through a 15-day subculture experiment without antibiotic selection pressure. Results For the first time,this study identified a linear plasmid in the genome of Enterococcus avium ZB195,which harbors the vancomycin resistance vanA gene and was capable of horizontal transfer to three recipient strains. Sequence alignment showed that the linear plasmid of ZB195 had the highest sequence identity with that of Enterococcus faecium AA708 from Japan,and phylogenetic analysis confirmed that they were most closely related. Simulation of global transmission trajectories revealed that the linear plasmid in Enterococcus was first detected in Japan in 2000,and then gradually spreaded to China,the United States,Norway,Denmark,India and other countries. Passage experiments indicated that the linear plasmid exhibited the highest stability in Enterococcus avium hosts. Conclusion The linear plasmids detected in Enterococcus strains in China may have originated from the horizontal transmission of Enterococcus faecium from Japan. Moreover,after transferring to Enterococcus avium,these plasmids can form better host adaptability. This suggests that it is necessary to strengthen cross-regional monitoring of linear plasmids in Enterococcus to curb the global spread of drug-resistant genes.