State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China.
BMC Vet Res. 2012 Aug 21;8:140. doi: 10.1186/1746-6148-8-140.
Extraintestinal pathogenic Escherichia coli (ExPEC) can cause a variety of infections outside the gastrointestinal tract in humans and animals. Infections due to swine ExPECs have been occurring with increasing frequency in China. These ExPECs may now be considered a new food-borne pathogen that causes cross-infections between humans and pigs. Knowledge of the clonal structure and virulence genes is needed as a framework to improve the understanding of phylogenetic traits of porcine ExPECs.
Multilocus sequence typing (MLST) data showed that the isolates investigated in this study could be placed into four main clonal complexes, designated as CC10, CC1687, CC88 and CC58. Strains within CC10 were classified as phylogroup A, and these accounted for most of our porcine ExPEC isolates. Isolates in the CC1687 clonal complex, formed by new sequence types (STs), was classified as phylogroup D, with CC88 isolates considered as B2 and CC58 isolates as B1. Porcine ExPECs in these four clonal complexes demonstrated significantly different virulence gene patterns. A few porcine ExPECs were indentified in phylogroup B2, the phylogroup in which human ExPECs mainly exist. However some STs in the four clonal groups of porcine ExPECs were reported to cause extraintestinal infections in human, based on data in the MLST database.
Porcine ExPECs have different virulence gene patterns for different clonal complexes. However, these strains are mostly fell in phylogenentic phylogroup A, B1 and D, which is different from human ExPECs that concentrate in phylogroup B2. Our findings provide a better understanding relating to the clonal structure of ExPECs in diseased pigs and indicate a need to re-evaluate their contribution to human ExPEC diseases.
肠外致病性大肠杆菌（ExPEC）可在人和动物的胃肠道以外引起多种感染。由猪源 ExPEC 引起的感染在中国日益增多。这些 ExPEC 现在可能被认为是一种新的食源性病原体，可导致人类和猪之间的交叉感染。了解克隆结构和毒力基因是作为了解猪源 ExPEC 系统发育特征的框架的必要条件。
多位点序列分型（MLST）数据显示，本研究中调查的分离株可分为四个主要克隆复合体，分别命名为 CC10、CC1687、CC88 和 CC58。CC10 内的菌株被分类为 A 群，这些菌株构成了我们大部分的猪源 ExPEC 分离株。CC1687 克隆复合体的分离株由新的序列型（ST）组成，被分类为 D 群，CC88 分离株被认为是 B2 群，CC58 分离株是 B1 群。这四个克隆复合体中的猪源 ExPEC 表现出明显不同的毒力基因模式。在 B2 群中发现了一些猪源 ExPEC，B2 群是人类 ExPEC 主要存在的群。然而，根据 MLST 数据库中的数据，四个猪源 ExPEC 克隆群的一些 ST 被报道可引起人类肠外感染。
不同克隆复合体的猪源 ExPEC 具有不同的毒力基因模式。然而，这些菌株主要属于系统发育 A 群、B1 群和 D 群，与集中在 B2 群的人类 ExPEC 不同。我们的研究结果提供了对患病猪 ExPEC 克隆结构的更好理解，并表明需要重新评估它们对人类 ExPEC 疾病的贡献。
