挪威首例散发型 VanD 型万古霉素耐药肠球菌中新型基因组岛和新型 vanD 亚型。
Novel genomic islands and a new vanD-subtype in the first sporadic VanD-type vancomycin resistant enterococci in Norway.
机构信息
Research Group for Host-Microbe Interactions, Department of Medical Biology, University of Tromsø (UiT) - The Arctic University of Norway, Tromsø, Norway.
Norwegian National Advisory Unit on Detection of Antimicrobial Resistance, Department of Microbiology and Infection Control, University Hospital of North-Norway, Tromsø, Norway.
出版信息
PLoS One. 2021 Jul 23;16(7):e0255187. doi: 10.1371/journal.pone.0255187. eCollection 2021.
BACKGROUND
Vancomycin-resistant enterococci (VRE) represent several types of transferable vancomycin resistance gene clusters. The vanD type, associated with moderate to high level vancomycin resistance, has only sporadically been described in clinical isolates. The aim of this study was to perform a genetic characterization of the first VanD-type VRE strains detected in Norway.
METHODS
The VanD-type VRE-strains (n = 6) from two patient cases were examined by antimicrobial susceptibility testing and whole genome sequencing (WGS) to uncover Van-phenotype, strain phylogeny, the vanD gene clusters, and their genetic surroundings. The putative transferability of vanD was examined by circularization PCR and filter mating.
RESULTS
The VanD-type Enterococcus faecium (n = 4) and Enterococcus casseliflavus (n = 2) strains recovered from two cases (A and B), expressed moderate to high level vancomycin resistance (MIC 64->256 mg/L) and various levels of teicoplanin susceptibility (MIC 2->256 mg/L). WGS analyses revealed phylogenetically different E. faecium strains (A1, A2, and A3 of case A and B1 from case B) as well as vanD gene clusters located on different novel genomic islands (GIs). The E. casseliflavus strains (B2 and B3 of case B) were not clonally related, but harbored nearly identical novel GIs. The vanD cluster of case B strains represents a novel vanD-subtype. All the vanD-GIs were integrated at the same chromosomal site and contained genes consistent with a Clostridiales origin. Circular forms of the vanD-GIs were detected in all strains except B1. Transfer of vanD to an E. faecium recipient was unsuccessful.
CONCLUSIONS
We describe the first VanD-type E. casseliflavus strains, a novel vanD-subtype, and three novel vanD-GIs with a genetic content consistent with a Clostridiales order origin. Despite temporal occurrence, case A and B E. faecium strains were phylogenetically diverse and harbored different vanD subtypes and vanD-GIs.
背景
耐万古霉素肠球菌（VRE）代表几种可转移的万古霉素耐药基因簇。VanD 型与中等到高水平的万古霉素耐药性相关，仅在临床分离株中偶尔描述过。本研究的目的是对在挪威首次检测到的 VanD 型 VRE 菌株进行遗传特征分析。
方法
对来自两例患者的 6 株 VanD 型 VRE 菌株进行药敏试验和全基因组测序（WGS），以揭示 Van 表型、菌株系统发育、vanD 基因簇及其遗传环境。通过环化 PCR 和滤膜交配检测 vanD 的潜在可转移性。
结果
从两例患者（A 和 B）中分离出的 VanD 型屎肠球菌（n=4）和粪肠球菌（n=2），表现出中等到高水平的万古霉素耐药性（MIC 64->256 mg/L）和不同水平的替考拉宁敏感性（MIC 2->256 mg/L）。WGS 分析揭示了来自 A 病例的具有不同进化关系的屎肠球菌菌株（A1、A2 和 A3）以及位于不同新型基因组岛（GI）上的 vanD 基因簇，以及来自 B 病例的 B2 和 B3 肠球菌菌株无克隆相关性，但携带几乎相同的新型 GI。B 病例的菌株的 vanD 簇代表一种新型的 vanD 亚型。所有的 vanD-GI 都整合在相同的染色体位点上，并且含有与梭菌目起源一致的基因。除了 B1 之外，所有菌株均检测到 vanD-GI 的环状形式。未能将 vanD 转移到屎肠球菌受体内。
结论
我们描述了首例 VanD 型粪肠球菌菌株、一种新型的 vanD 亚型以及三个具有与梭菌目起源一致的遗传内容的新型 vanD-GI。尽管发生时间不同，但 A 和 B 病例的屎肠球菌菌株在系统发育上是多样化的，携带不同的 vanD 亚型和 vanD-GI。
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