Li J, Li B, Ni Y, Sun J
Department of Clinical Microbiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, 197 Ruijin 2nd Rd, Shanghai, 200025, China.
Eur J Clin Microbiol Infect Dis. 2015 Mar;34(3):447-51. doi: 10.1007/s10096-014-2244-2. Epub 2014 Sep 25.
Shigellosis is a public health concern in China. We tested 216 Shigella isolates collected in Shanghai in 2007 for the production of extended-spectrum beta-lactamases (ESBLs). ESBL-producing isolates were characterized using polymerase chain reaction (PCR)-based genotyping, conjugation, pulsed-field gel electrophoresis (PFGE), and DNA sequence analysis of regions adjacent to bla genes. Plasmids containing genes encoding ESBLs were analyzed using plasmid replicon typing. ESBLs were produced by 18.1 % (39/216) of Shigella isolates, and all 39 ESBL-producing strains harbored bla CTX-M genes. CTX-M-14 was the most frequent variant (69.2 %, 27/39), followed by CTX-M-15 (15.4 %, 6/39). All bla CTX-M genes were transferable by conjugation, and the insertion sequence ISEcp1 was detected upstream of all bla CTX-M genes. The CTX-M-producing Shigella isolates showed high clonal diversity. IncI1, IncFII, IncN, and IncB/O replicons were respectively detected in 23 (58.9 %), 9 (23.1 %), 1 (2.6 %), and 1 (2.6 %) of the 39 transconjugants carrying bla CTX-M. The bla CTX-M-14 genes were most frequently carried by IncI1 (n = 13, 48.1 %) or IncFII (n = 9, 33.3 %) plasmids, and the bla CTX-M-15 genes were closely associated with IncI1 (n = 5, 83.3 %). Our findings demonstrate the high prevalence of ESBL-producing Shigella in Shanghai, the importance of plasmids and ISEcp1 as carriers of bla CTX-M genes, and the close association between certain bla CTX-M genes with a specific plasmid.
志贺菌病是中国的一个公共卫生问题。我们检测了2007年在上海收集的216株志贺菌分离株产超广谱β-内酰胺酶（ESBLs）的情况。利用基于聚合酶链反应（PCR）的基因分型、接合试验、脉冲场凝胶电泳（PFGE）以及bla基因邻近区域的DNA序列分析对产ESBLs的分离株进行特征分析。使用质粒复制子分型法对携带编码ESBLs基因的质粒进行分析。18.1%（39/216）的志贺菌分离株产ESBLs，所有39株产ESBLs的菌株均携带blaCTX-M基因。CTX-M-14是最常见的变异型（69.2%，27/39），其次是CTX-M-15（15.4%，6/39）。所有blaCTX-M基因均可通过接合转移，并且在所有blaCTX-M基因上游均检测到插入序列ISEcp1。产CTX-M的志贺菌分离株显示出高度的克隆多样性。在携带blaCTX-M的39株接合子中，分别检测到IncI1、IncFII、IncN和IncB/O复制子，比例分别为23株（58.9%）、9株（23.1%）、1株（2.6%）和1株（2.6%）。blaCTX-M-14基因最常见于IncI1质粒（n = 13，48.1%）或IncFII质粒（n = 9，33.3%），而blaCTX-M-15基因与IncI1密切相关（n = 5，83.3%）。我们的研究结果表明，上海产ESBLs的志贺菌流行率很高，质粒和ISEcp1作为blaCTX-M基因载体的重要性，以及某些blaCTX-M基因与特定质粒之间的密切关联。
