Frederiksen Rikki Franklin, Urdahl Anne Margrete, Slettemeås Jannice Schau, Granstad Silje, Simm Roger, Lagesen Karin
Department of Animal Health and Food Safety, Norwegian Veterinary Institute, Ås, Norway.
Department of Biosciences, University of Oslo, Oslo, Norway.
PLoS One. 2025 Jun 4;20(6):e0324789. doi: 10.1371/journal.pone.0324789. eCollection 2025.
Vancomycin resistant enterococci (VRE) are a globally leading cause of nosocomial infections in humans, and a potential animal VRE reservoir, especially in poultry, is of concern. It has been suggested that the presence of VRE in broilers has been prolonged due to co-selection of narasin resistance (narAB genes) and vancomycin resistance (vanA genes), and that these genes may be present on the same plasmids. The aim of this study was to use whole genome sequencing to characterize and compare both the chromosomes and plasmids of VRE isolates from poultry in Norway, and to elucidate whether co-localisation of narAB and vanA genes on the same genetic elements, or clonal spread, could explain the persistence of VRE. A total of 30 VRE isolates from the years 2002-2013 were included, 23 from broiler flocks and seven from turkey flocks. WGS analyses showed that the isolates were genetically diverse with the number of SNPs ranging from 10 to 2807. The isolates belonged to 15 different sequence types, though all carried a plasmid similar to pVEF plasmids, and contained both vanA and narAB. A comparative gene analysis indicated that narAB is carried on a composite transposon, and that interspecies transfer of the plasmid between Enterococcus faecium and Enterococcus hirae may occur. The absence of transfer genes on the pVEF-like plasmids and their presence on a megaplasmid suggest that the megaplasmid probably act as a helper plasmid. Overall, the results support that the use of narasin in broilers may be a risk factor for a persistent reservoir of VRE in broilers.
耐万古霉素肠球菌（VRE）是全球人类医院感染的主要原因，尤其是家禽中潜在的VRE储存库令人担忧。有人认为，肉鸡中VRE的存在因耐那拉菌素（narAB基因）和耐万古霉素（vanA基因）的共同选择而延长，且这些基因可能存在于同一质粒上。本研究的目的是利用全基因组测序对挪威家禽VRE分离株的染色体和质粒进行表征和比较，并阐明narAB和vanA基因在同一遗传元件上的共定位或克隆传播是否可以解释VRE的持续存在。共纳入了2002年至2013年期间的30株VRE分离株，其中23株来自肉鸡群，7株来自火鸡群。全基因组测序分析表明，这些分离株在遗传上具有多样性，单核苷酸多态性（SNP）数量从10到2807不等。这些分离株属于15种不同的序列类型，尽管它们都携带一种类似于pVEF质粒的质粒，并且同时含有vanA和narAB。比较基因分析表明，narAB位于一个复合转座子上，粪肠球菌和希拉肠球菌之间可能发生该质粒的种间转移。pVEF样质粒上不存在转移基因，而在一个大质粒上存在，这表明该大质粒可能起到辅助质粒的作用。总体而言，结果支持在肉鸡中使用那拉菌素可能是肉鸡中VRE持续存在储存库的一个风险因素。
