State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital of Medicine School, Zhejiang University, Hangzhou, China.
Department of Laboratory Medicine, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing, Jiangsu, China.
J Antimicrob Chemother. 2018 Jan 1;73(1):66-76. doi: 10.1093/jac/dkx361.
To investigate the population structure, drug resistance mechanisms and plasmids of community-associated Enterobacter cloacae complex (CA-ECC) isolates in China.
Sixty-two CA-ECC isolates collected from 31 hospitals across China were typed by hsp60 typing and MLST. ESBL and AmpC-overexpression phenotype was determined by double-disc synergy test. Replicon typing and conjugation were performed for plasmid analysis. All ESBL-positive isolates and representative conjugants were subjected to detailed characterization by WGS.
Enterobacter hormaechei and Enterobacter kobei were predominant in our collections. MLST distinguished 46 STs with a polyclonal structure. ST591 was the most prevalent clone detected in northern China. Twenty-two isolates (35.5%) were ESBL positive and half of them were E. kobei. ESBL positivity was related to ESBL production (15/22) and to AmpC overexpression (18/22). Core-genome phylogenetic analysis identified intra- and inter-regional dissemination of ESBL-producing E. kobei clones. ESBL producers were exclusively classified as E. hormaechei and E. kobei, and blaCTX-M-3 was the most prevalent ESBL genotype (10/15) detected in four different environments. In the ESBL-positive population, the ESBL producers encoded more drug resistance genes (8-24 genes) by carrying more plasmids (1-3 plasmids) than the non-ESBL-producing isolates, resulting in an inter-group difference in drug susceptibilities. IncHI-type plasmids were prevalent in the ESBL producers (12/15). All IncHI2-type plasmids (n = 11) carried ESBL genes and shared a similar backbone to p09-036813-1A_261 recovered from Salmonella enterica in Canada.
The species-specific distribution, species-dependent ESBL mechanism and endemic plasmids identified in our study highlight the necessity for tailored surveillance of CA-ECC in the future.
研究中国社区获得性阴沟肠杆菌复合体（CA-ECC）分离株的种群结构、耐药机制和质粒。
采用 hsp60 分型和 MLST 对来自中国 31 家医院的 62 株 CA-ECC 分离株进行分型。通过双碟协同试验确定 ESBL 和 AmpC 过表达表型。进行复制子分型和接合实验进行质粒分析。对所有 ESBL 阳性分离株和代表性接合子进行 WGS 进行详细特征分析。
肠杆菌属和肠杆菌属在我们的研究中占主导地位。MLST 将 46 个 ST 分为多克隆结构。ST591 是在中国北方检测到的最流行的克隆。22 株（35.5%）为 ESBL 阳性，其中一半为肠杆菌属。ESBL 阳性与 ESBL 产生（15/22）和 AmpC 过表达（18/22）有关。核心基因组系统发育分析确定了产 ESBL 肠杆菌属克隆的区内和区际传播。ESBL 阳性分离株均被归类为肠杆菌属和肠杆菌属，blaCTX-M-3 是四种不同环境中检测到的最常见的 ESBL 基因型（10/15）。在 ESBL 阳性人群中，ESBL 阳性分离株携带更多的耐药基因（8-24 个基因）和更多的质粒（1-3 个质粒），导致药物敏感性的组间差异。IncHI 型质粒在 ESBL 阳性分离株中较为普遍（12/15）。所有 IncHI2 型质粒（n=11）均携带 ESBL 基因，并与从加拿大沙门氏菌中回收的 p09-036813-1A_261 具有相似的骨架。
本研究中鉴定的种特异性分布、种依赖性 ESBL 机制和地方性质粒，强调了未来对 CA-ECC 进行针对性监测的必要性。
