Tian Guo-Bao, Huang Ying-Min, Fang Zhi-Li, Qing Yun, Zhang Xue-Fei, Huang Xi
Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou 510080, China Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.
Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, 74 Zhongshan 2nd Road, Guangzhou 510080, China Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou 510060, China.
J Antimicrob Chemother. 2014 Aug;69(8):2081-5. doi: 10.1093/jac/dku126. Epub 2014 Apr 28.
To characterize a novel CTX-M chimera, CTX-M-137, from Escherichia coli clinical isolates in China.
Isolates were collected from five hospitals between 22 February 2009 and 20 December 2011. Resistance genes were investigated by PCR. blaCTX-M-137 was cloned and purified for kinetic measurements. Conjugation experiments, S1-PFGE and Southern blotting were performed to study the plasmid harbouring blaCTX-M-137. The genetic environment of blaCTX-M-137 was determined by genomic cloning and sequencing.
A total of 247 cephalosporin-resistant E. coli were identified. blaCTX-M group genes were the most prevalent extended-spectrum β-lactamase (ESBL) genes, with 71 isolates harbouring blaCTX-M-1 group genes and 137 isolates harbouring blaCTX-M-9 group genes. A novel chimera of CTX-M-14-like and CTX-M-15-like ESBLs, designated CTX-M-137, was identified from a 60-year-old man with a urinary tract infection. The N-terminus of CTX-M-137 matched CTX-M-14 and the C-terminus matched CTX-M-15. CTX-M-137 conferred resistance to ceftazidime, cefotaxime and aztreonam. Purified CTX-M-137 showed good hydrolytic activity against ceftazidime and cefotaxime, and was inhibited by clavulanic acid. The blaCTX-M-137 was carried on an ∼83 kb IncI1 plasmid. blaCTX-M-137 was carried on a complete transposition unit ISEcp1-blaCTX-M-137-Δorf477 inserted into yagA, which is part of the IncI1 plasmid backbone.
We identified a novel CTX-M chimera, CTX-M-137, with a CTX-M-14-like N-terminus and a CTX-M-15-like C-terminus. Our findings suggest an ongoing diversification of CTX-M-type ESBLs through recombination events.
鉴定一株来自中国临床分离大肠埃希菌的新型CTX-M嵌合体CTX-M-137。
于2009年2月22日至2011年12月20日期间从5家医院收集分离菌株。采用聚合酶链反应（PCR）检测耐药基因。克隆并纯化blaCTX-M-137用于动力学测定。进行接合试验、S1-脉冲场凝胶电泳（PFGE）和Southern杂交以研究携带blaCTX-M-137的质粒。通过基因组克隆和测序确定blaCTX-M-137的基因环境。
共鉴定出247株对头孢菌素耐药的大肠埃希菌。blaCTX-M组基因是最常见的超广谱β-内酰胺酶（ESBL）基因，71株携带blaCTX-M-1组基因，137株携带blaCTX-M-9组基因。从一名60岁的尿路感染男性患者中鉴定出一种新型的CTX-M-14样和CTX-M-15样ESBL嵌合体，命名为CTX-M-137。CTX-M-137的N端与CTX-M-14匹配，C端与CTX-M-15匹配。CTX-M-137对头孢他啶、头孢噻肟和氨曲南耐药。纯化后的CTX-M-137对头孢他啶和头孢噻肟显示出良好的水解活性，并被克拉维酸抑制。blaCTX-M-137位于一个约83 kb的IncI1质粒上。blaCTX-M-137位于一个完整的转座单元ISEcp1-blaCTX-M-137-Δorf477上，该转座单元插入到yagA中，yagA是IncI1质粒骨架的一部分。
我们鉴定出一种新型的CTX-M嵌合体CTX-M-137，其N端类似CTX-M-14，C端类似CTX-M-15。我们的研究结果表明，CTX-M型ESBLs通过重组事件不断发生多样化。
