Jiang Wei, Men Shuai, Kong Linghan, Ma Suzhen, Yang Yongqiang, Wang Yongxiang, Yuan Qiwu, Cheng Guangyang, Zou Wencheng, Wang Hongning
1 Key Laboratory of Bio-Resources and Eco-Environment, Ministry of Education, College of Life Science, Sichuan University , Chengdu, China .
2 Animal Disease Prevention and Food Safety Key Laboratory of Sichuan Province , Chengdu, China .
Foodborne Pathog Dis. 2017 Apr;14(4):210-218. doi: 10.1089/fpd.2016.2230. Epub 2017 Feb 17.
The aim of this study was to investigate the prevalence of fosfomycin resistance gene fosA3 and characterize plasmids harboring fosA3 among CTX-M-producing Escherichia coli from chickens in China. A total of 234 CTX-M-producing E. coli isolates collected from chickens from 2014 to 2016 were screened for the presence of plasmid-mediated fosfomycin resistance genes (fosA, fosA3, and fosC2). Clonal relatedness of fosA3-positive isolates was determined by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). The genetic environment of fosA3 was analyzed by polymerase chain reaction (PCR) mapping. Plasmids were studied by using conjugation experiments, PCR-based replicon typing and plasmid MLST. Sixty-four (27.4%) fosA3-positive E. coli isolates were identified in this study. The gene bla (31/64) was predominant among these strains, followed by bla (18/64) and bla (14/64). Various PFGE patterns and sequence types (STs) indicated that these isolates were clonally unrelated. Seven different genetic environments of fosA3 were identified and two new combinations (ISEcp1-bla-ΔIS903D-IS26-fosA3-orf1-orf2-Δorf3-IS26 and IS26-ISEcp1-bla-orf477-bla-IS26-fosA3-orf1-orf2-Δorf3-IS26) were discovered for the first time. Conjugation experiments were successful for 47 isolates and 33 transconjugants harbored a single plasmid. Plasmids carrying fosA3 belonged to incompatibility group IncFII (17/33), IncI1 (2/33), IncHI2 (3/33), and IncB/O (1/33). F33:A-:B- plasmids carrying bla, IncHI2/ST3 plasmids carrying bla, and F2:A-:B-plasmids carrying bla were found in E. coli isolates from different provinces. Our results revealed a considerable prevalence of fosA3 gene among CTX-M-producing E. coli with clonal diversity from chickens in China. The transmission of different kinds of plasmids is responsible for the dissemination of fosA3 in chicken farms in China.
本研究旨在调查磷霉素耐药基因fosA3的流行情况，并对中国鸡源产CTX-M大肠埃希菌中携带fosA3的质粒进行特征分析。对2014年至2016年从鸡中收集的234株产CTX-M大肠埃希菌分离株进行筛选，以检测质粒介导的磷霉素耐药基因（fosA、fosA3和fosC2）的存在情况。通过脉冲场凝胶电泳（PFGE）和多位点序列分型（MLST）确定fosA3阳性分离株的克隆相关性。通过聚合酶链反应（PCR）图谱分析fosA3的基因环境。利用接合实验、基于PCR的复制子分型和质粒MLST对质粒进行研究。本研究共鉴定出64株（27.4%）fosA3阳性大肠埃希菌分离株。这些菌株中bla基因（31/64）占主导地位，其次是bla基因（18/64）和bla基因（14/64）。各种PFGE图谱和序列类型（STs）表明这些分离株在克隆上不相关。鉴定出7种不同的fosA3基因环境，首次发现两种新的组合（ISEcp1-bla-ΔIS903D-IS26-fosA3-orf1-orf2-Δorf3-IS26和IS26-ISEcp1-bla-orf477-bla-IS26-fosA3-orf1-orf2-Δorf3-IS26）。47株分离株的接合实验成功，33株接合子携带单个质粒。携带fosA3的质粒属于不相容群IncFII（17/33）、IncI1（2/33）、IncHI2（3/33）和IncB/O（1/33）。在来自不同省份的大肠埃希菌分离株中发现了携带bla的F33:A-:B-质粒、携带bla的IncHI2/ST3质粒和携带bla的F2:A-:B-质粒。我们的结果显示，在中国鸡源产CTX-M大肠埃希菌中，fosA3基因相当普遍，且具有克隆多样性。不同类型质粒的传播导致了fosA3在中国养鸡场中的扩散。
