Department of Laboratory Medicine, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, 321# Zhongshan Road, Gulou District, Nanjing, Jiangsu Province 210008, PR China.
Department of Laboratory Medicine, Jiangning District Hospital of Traditional Chinese Medicine, 657# Tianyin Avenue, Jiangning District, Nanjing, Jiangsu Province 211100, PR China.
J Glob Antimicrob Resist. 2019 Jun;17:180-186. doi: 10.1016/j.jgar.2019.01.001. Epub 2019 Jan 11.
Linezolid-resistant Enterococcus have spread worldwide. This study investigated the prevalence of linezolid-non-susceptible Enterococcus (LNSE) and the potential mechanism and molecular epidemiology of LNSE isolates from Nanjing, China.
Linezolid susceptibility of 2555 Enterococcus was retrospectively determined by Etest. Vancomycin and teicoplanin MICs were determined for LNSE by Etest. PCR and DNA sequencing were used to investigate the potential molecular mechanism. Clonal relatedness between LNSE isolates was analysed by MLST. WGS was also performed.
A total of 27 Enterococcus isolates (24 Enterococcus faecalis, 3 Enterococcus faecium) with linezolid MICs of 4-48μg/mL were identified, among which 20 E. faecalis and 3 E. faecium were positive for optrA. No mutations were found in genes encoding domain V of 23S rRNA or ribosomal proteins L3/L4; the cfr gene was not found. The 24 linezolid-non-susceptible E. faecalis were classified into eight STs (ST16, ST480, ST476, ST631, ST585, ST428, ST25 and ST689). The three linezolid-non-susceptible E. faecium were classified as ST17, ST400 and ST195. Comparison of the deduced OptrA amino acid sequences of the 23 optrA-positive isolates by PCR-based sequencing and WGS with that of the original OptrA from E. faecalis E349 revealed seven variants (KD, EDP, EDM, D, EDD, RDK and DP) in 16 isolates, with no mutations in the remaining 7 isolates. optrA was found downstream of fexA by searching the pE349 sequence based on WGS data.
Emergence of LNSE with optrA-mediated resistance and clonal dissemination of ST16 E. faecalis in our hospital may pose a potential public-health threat.
耐(linezolid)利福霉素肠球菌已在全球范围内传播。本研究调查了中国南京耐利福霉素肠球菌（LNSE）的流行情况及其潜在的机制和分子流行病学。
通过 Etest 法回顾性测定 2555 株肠球菌对利福霉素的敏感性。用 Etest 法测定 LNSE 的万古霉素和替考拉宁 MIC。通过 PCR 和 DNA 测序检测潜在的分子机制。通过 MLST 分析 LNSE 分离株的克隆相关性。还进行了 WGS。
共鉴定出 27 株利福霉素 MIC 为 4-48μg/ml 的肠球菌分离株（24 株粪肠球菌，3 株屎肠球菌），其中 20 株粪肠球菌和 3 株屎肠球菌 optrA 阳性。在编码 23S rRNA 或核糖体蛋白 L3/L4 结构域 V 的基因中未发现突变；未发现 cfr 基因。24 株耐利福霉素的粪肠球菌分为 8 个 ST（ST16、ST480、ST476、ST631、ST585、ST428、ST25 和 ST689）。3 株耐利福霉素的屎肠球菌分为 ST17、ST400 和 ST195。通过 PCR 测序和 WGS 对 23 株 optrA 阳性分离株的 OptrA 氨基酸序列进行推导比较，与 E. faecalis E349 原始 OptrA 相比，16 株中有 7 种变异（KD、EDP、EDM、D、EDD、RDK 和 DP），其余 7 株无突变。根据 WGS 数据搜索 pE349 序列，发现 optrA 位于 fexA 下游。
我院耐利福霉素肠球菌的出现和 ST16 粪肠球菌的克隆传播可能对公共卫生构成潜在威胁。
