State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, 150069, PR China.
State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, 150069, PR China.
Vet Microbiol. 2018 Apr;217:53-57. doi: 10.1016/j.vetmic.2018.02.003. Epub 2018 Feb 6.
The objective of this study was to investigate the prevalence of the cfr gene in Escherichia coli isolates from domestic animals in Northeast China and to characterize the cfr-containing plasmids. Between June 2015 and April 2016, 370 E. coli isolates were collected from pigs, chickens, and dairy cows in Northeast China. Among these, 111 were florfenicol resistant, including 109 isolates carrying the floR gene and 6 positives for cfr. The prevalence of cfr in E. coli isolates from the four northeast provinces in China was 1.6% (6/370), which was higher than that previously reported (0.08% and 0.5%). All six cfr-containing E. coli isolates were highly resistant to florfenicol (100%), cefotaxime (100%), and fosfomycin (100%). Complete sequence analysis of two cfr-carrying plasmids revealed high homology of the IncX4-type pEC14cfr plasmid with two other cfr-harboring plasmids, pSD11 and pGXEC6, found in swine E. coli isolates from southern China. pEC14cfr-like plasmids have been isolated in five provinces in southern and northern China. The isolation sites were up to 2700 kilometers apart, implying that pEC14cfr-like plasmids are likely to be national epidemic cfr-carrying plasmids that mediate the dissemination of cfr in China. Moreover, the genetic structure (IS26-IS26-cfr-rec-pre/mob-ramA-IS26) of the second cfr-carrying plasmid, IncF14:A-:B- pEC295cfr, represents a novel genetic environment for cfr identified for the first time in the present study. Sequence homology analysis indicated that the cfr-carrying element was most likely introduced into a cfr-negative pEC12 plasmid backbone, which evolved into the cfr-carrying vector, pEC295cfr. Moreover, isolation of the IncF14:A-:B- pEC295cfr plasmid harboring cfr suggests that IncFII plasmids maybe have become additional effective vehicles for cfr dissemination. These results highlight the importance of surveying the prevalence of IncX4 and IncFII plasmids in gram-negative bacteria, especially in swine E. coli isolates.
本研究的目的是调查中国东北地区家畜源大肠杆菌中 cfr 基因的流行情况，并对携带 cfr 的质粒进行特征分析。2015 年 6 月至 2016 年 4 月，从中国东北地区的猪、鸡和奶牛中采集了 370 株大肠杆菌。其中，111 株对氟苯尼考耐药，包括 109 株携带 floR 基因和 6 株 cfr 阳性。中国东北四省大肠杆菌中 cfr 的检出率为 1.6%（6/370），高于以往报道（0.08%和 0.5%）。6 株携带 cfr 的大肠杆菌对氟苯尼考（100%）、头孢噻肟（100%）和磷霉素（100%）高度耐药。对携带 cfr 的两个质粒的完整序列分析表明，IncX4 型 pEC14cfr 质粒与中国南方猪源大肠杆菌中携带的另外两个 cfr 质粒 pSD11 和 pGXEC6 具有高度同源性。pEC14cfr 样质粒已在南方和北方五个省分离出来。分离地点相距 2700 公里，这意味着 pEC14cfr 样质粒可能是中国传播 cfr 的全国性流行 cfr 携带质粒。此外，第二个携带 cfr 的质粒，IncF14:A-:B- pEC295cfr 的遗传结构（IS26-IS26-cfr-rec-pre/mob-ramA-IS26）是本研究首次确定的新型 cfr 遗传环境。序列同源性分析表明，cfr 携带元件很可能被引入到 cfr 阴性的 pEC12 质粒骨架中，进而进化为 cfr 携带载体 pEC295cfr。此外，携带 IncF14:A-:B- pEC295cfr 质粒的 cfr 分离表明，IncFII 质粒可能已成为 cfr 传播的另一种有效载体。这些结果强调了调查革兰氏阴性菌，尤其是猪源大肠杆菌中 IncX4 和 IncFII 质粒流行情况的重要性。
