Jiang Han, Cheng Hui, Liang Yi, Yu Shengtao, Yu Ting, Fang Jiehong, Zhu Cheng
Key Laboratory of Marine Food Quality and Hazard Controlling Technology of Zhejiang Province, College of Life Sciences, China Jiliang University, Hangzhou, China.
Front Microbiol. 2019 Aug 2;10:1787. doi: 10.3389/fmicb.2019.01787. eCollection 2019.
High prevalence rates of sulfonamide resistance genes , , and have been observed in Gram-negative bacteria isolated from humans, domestic animals, and aquaculture species worldwide. We investigated the distribution characteristics, location, conjugative transferability, and genetic environments of genes from isolates collected from and pork samples from three large markets in Zhejiang, China. The prevalence rates of genes in sulfonamide-resistant isolates from and pork samples were 90.0 and 88.6%, respectively, and the prevalence of and was significantly higher than that of ( < 0.05). Twenty-four representative -positive isolates were analyzed in detail. Southern blot hybridization confirmed that genes of isolates were located on plasmids and/or chromosomes. Transfer of resistance through conjugation was observed in all 18 isolates harboring genes on plasmids. Replicon typing identified seven different incompatibility groups and IncF was the dominant replicon type among gene-containing plasmids from both sources. PCR walking analysis indicated that 87.5% (35/40) of gene-related fragments carried insertion sequences (ISs) belonging to a variety of families in diverse sites, with IS occurring most frequently. In addition, the gene was detected mainly in fragments carrying class 1 integrons. Co-location on the same fragment with resistance genes that may contribute to the persistence and dissemination of and/or genes. The diversity of mobile genetic elements and resistance genes adjacent to was much lower than those adjacent to and , especially those located in chromosomes, which reduced the transmission potential of the gene. In conclusion, combined with the results of clonal relatedness analysis by PFGE and MLST of 24 representative isolates from and pork samples, it showed that a small number of genes were vertically transmitted among from and that horizontal gene transfer was likely the main transmission mechanism of genes from both sources. Our results provide important information to better understand the risk of transmission of genes from seafood and meat to humans.
在全球范围内从人类、家畜和水产养殖物种中分离出的革兰氏阴性菌中，已观察到磺胺类耐药基因、和的高流行率。我们调查了从中国浙江三个大型市场的海鲜和猪肉样本中收集的分离株中基因的分布特征、位置、接合转移性和遗传环境。海鲜和猪肉样本中磺胺类耐药分离株中基因的流行率分别为90.0%和88.6%，和的流行率显著高于（<0.05）。对24株具有代表性的阳性分离株进行了详细分析。Southern印迹杂交证实分离株的基因位于质粒和/或染色体上。在所有18株质粒上携带基因的分离株中均观察到通过接合进行的耐药性转移。复制子分型鉴定出七个不同的不相容群，IncF是来自这两个来源的含基因质粒中的主要复制子类型。PCR步移分析表明，87.5%（35/40）的基因相关片段在不同位点携带属于各种家族的插入序列（IS），其中IS出现最为频繁。此外，基因主要在携带1类整合子的片段中检测到。与可能有助于和/或基因持久性和传播的耐药基因共定位在同一片段上。与和相邻的移动遗传元件和耐药基因的多样性远低于与相邻的，尤其是位于染色体上的那些，这降低了基因的传播潜力。总之，结合对24株来自海鲜和猪肉样本的具有代表性的分离株进行PFGE和MLST克隆相关性分析的结果，表明少数基因在海鲜来源的分离株之间垂直传播，水平基因转移可能是这两个来源基因的主要传播机制。我们的结果为更好地了解海鲜和肉类中基因向人类传播的风险提供了重要信息。
