Department of Medical Laboratory, Chang Gung Memorial Hospital, Taoyuan, Taiwan; Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan; Research Center for Pathogenic Bacteria, Chang Gung University, Taoyuan, Taiwan.
J Microbiol Immunol Infect. 2018 Dec;51(6):821-828. doi: 10.1016/j.jmii.2018.08.008. Epub 2018 Aug 27.
BACKGROUND/PURPOSES: Vancomycin resistance increased significantly to 31.3% among Enterococcus faecium in 2006 and remained high thereafter at a university hospital in Taiwan. A longitudinal study was retrospectively conducted to characterize these vancomycin-resistant E. faecium (VRE-fm).
A total of 378 non-repetitive VRE-fm blood isolates collected during 2002-2015 were studied. Multilocus sequence typing, pulsed-field gel electrophoresis, analysis of van genes and the Tn1546 structure, and conjugation experiments were performed.
The majority (78.0%) of the isolates were associated with hospital-acquired infections. Molecular typing revealed nine major pulsotypes and five predominant sequence types (STs): ST17 (33.9%), ST78 (18.3%), ST414 (14.6%), ST18 (10.6%), and ST203 (7.4%). Fluctuation of these prevailing STs among the study years in association with some major pulsotypes was noted. All isolates carried vanA genes, except that in four isolates vanB genes were found. Among the vanA-carrying Tn1546-like elements, one predominant structure type (Type I, 55.9%) was noted throughout the study years. Since 2009, another predominant structure type (Type II, 40.1%) has emerged firstly in ST414 and gradually spread to other 11 STs in subsequent years. Isolates carrying these Type II Tn1546-like elements have become the most predominant population since 2014, majorly found in ST78 and ST17. Preliminary experiments indicated that plasmids carrying the Type II Tn1546-like elements demonstrated ten-fold higher efficiency than those carrying the Type I Tn1546-like elements.
Dissemination of some major STs and horizontal transfer of plasmids carrying two major structure types of Tn1546-like elements may have together contributed to the increase of VRE-fm infection.
背景/目的：2006 年，台湾一家大学医院的屎肠球菌中万古霉素耐药性显著上升至 31.3%，此后一直居高不下。本研究对万古霉素耐药屎肠球菌（VRE-fm）进行了回顾性纵向研究。
研究共纳入 2002-2015 年采集的 378 株非重复 VRE-fm 血培养分离株。进行多位点序列分型、脉冲场凝胶电泳、分析 van 基因和 Tn1546 结构以及接合实验。
大多数（78.0%）分离株与医院获得性感染有关。分子分型显示 9 种主要脉冲场凝胶电泳型和 5 种主要序列型（ST）：ST17（33.9%）、ST78（18.3%）、ST414（14.6%）、ST18（10.6%）和 ST203（7.4%）。研究期间，一些主要脉冲场凝胶电泳型与主要 ST 之间存在波动。所有分离株均携带 vanA 基因，除 4 株分离株携带 vanB 基因外。在携带 vanA 的 Tn1546 样元件中，整个研究期间均发现一种主要结构类型（I 型，55.9%）。自 2009 年以来，另一种主要结构类型（II 型，40.1%）首先出现在 ST414 中，并在随后几年逐渐传播到其他 11 种 ST。自 2014 年以来，携带这些 II 型 Tn1546 样元件的分离株成为最主要的流行株，主要见于 ST78 和 ST17。初步实验表明，携带 II 型 Tn1546 样元件的质粒比携带 I 型 Tn1546 样元件的质粒效率高 10 倍。
一些主要 ST 的传播和携带两种主要 Tn1546 样元件结构类型的质粒的水平转移可能共同导致 VRE-fm 感染的增加。
