Vancomycin variable Enterococcus (VVE) bacteria are phenotypically susceptible to vancomycin, but they harbor the vanA gene. We aimed to ascertain the prevalence of VVE among clinically isolated vancomycin-susceptible Enterococcus faecium (VSE) isolates, as well as elucidate the molecular characteristics of the vanA gene cluster within these isolates. Notably, we investigated the prevalence and structure of the vanA gene cluster of VVE. Between June 2021 and May 2022, we collected consecutive, non-duplicated vancomycin-susceptible Enterococcus faecium (VSE) samples. Real-time PCR was performed to detect the presence of vanA, vanB, and vanC. Overlapping PCR with sequencing and whole-genome sequencing were performed for structural analysis. Sequence types (STs) were determined by multilocus sequence typing. Exposure testing was performed to assess the ability of the isolates to acquire vancomycin resistance. Among 282 VSE isolates tested, 20 isolates (7.1%) were VVE. Among them, 17 isolates had partial deletions in the IS1216 or IS1542 sequences in vanS (N=10), vanR (N=5), or vanH (N=2). All VVE isolates belonged to the CC17 complex and comprised five STs, namely ST17 (40.0%), ST1421 (25.0%), ST80 (25.0%), ST787 (5.0%), and ST981 (5.0%). Most isolates were related to three hospital-associated clones (ST17, ST1421, and ST80). After vancomycin exposure, 18 of the 20 VVEs acquired vancomycin resistance. Considering the high reversion rate, detecting VVE by screening VSE for vanA is critical for appropriate treatment and infection control.

中文翻译：

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从临床标本中分离出万古霉素变异屎肠球菌的流行率和分子特征。


万古霉素变异肠球菌 (VVE) 细菌在表型上对万古霉素敏感，但它们带有 vanA 基因。我们的目的是确定临床分离的万古霉素敏感屎肠球菌 (VSE) 分离株中 VVE 的患病率，并阐明这些分离株内 vanA 基因簇的分子特征。值得注意的是，我们研究了 VVE vanA 基因簇的流行率和结构。 2021 年 6 月至 2022 年 5 月期间，我们收集了连续、非重复的万古霉素敏感屎肠球菌 (VSE) 样本。进行实时 PCR 检测 vanA、vanB 和 vanC 的存在。采用重叠 PCR 测序和全基因组测序进行结构分析。序列类型（ST）由多位点序列分型确定。进行暴露测试以评估分离株获得万古霉素耐药性的能力。在测试的 282 个 VSE 分离株中，20 个分离株 (7.1%) 为 VVE。其中，17个分离株在vanS（N=10）、vanR（N=5）或vanH（N=2）中IS1216或IS1542序列部分缺失。所有 VVE 分离株均属于 CC17 复合体，包含 5 个 ST，即 ST17 (40.0%)、ST1421 (25.0%)、ST80 (25.0%)、ST787 (5.0%) 和 ST981 (5.0%)。大多数分离株与三个医院相关克隆（ST17、ST1421 和 ST80）相关。暴露于万古霉素后，20 个 VVE 中有 18 个获得了万古霉素耐药性。考虑到高回复率，通过筛选 VSE 中的 vanA 来检测 VVE 对于适当的治疗和感染控制至关重要。