National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, China; Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou 510642, China.
National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, China; Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou 510642, China; Jiangsu Co-Innovation Center for the Prevention and Control of Important Animal Infectious Disease and Zoonoses Yangzhou University, China.
Vet Microbiol. 2024 Sep;296:110171. doi: 10.1016/j.vetmic.2024.110171. Epub 2024 Jul 2.
Intestinal pathogenic Escherichia coli (InPEC) is one of the most common causes of bacterial diarrhea in farm animals, including profuse neonatal diarrhea and post weaning diarrhea (PWD) in piglets. In this study, we investigated the prevalence of InPEC and associated primary virulence factors among 543 non-duplicate E. coli isolates from diarrheal pigs from 15 swine farms in southern China. Six major virulence genes associated with InPEC were identified among 69 (12.71 %) E. coli isolates and included est (6.62 %), K88 (4.79 %), elt (3.68 %), eae (1.47 %), stx2 (0.92 %) and F18 (0.55 %). Three pathotypes of InPEC were identified including ETEC (8.10 %), EPEC (1.29 %) and STEC/ETEC (0.92 %). In particular, K88 was only found in ETEC from breeding farms, whereas F18 was only present in STEC/ETEC hybrid from finishing farms. Whole genome sequence analysis of 37 E. coli isolates revealed that InPEC strains frequently co-carried multiple antibiotic resistance gene (ARG). est, elt and F18 were also found to co-locate with ARGs on a single IncFIB/IncFII plasmid. InPEC isolates from different pathotypes also possessed different profiles of virulence genes and antimicrobial resistance genes. Population structure analysis demonstrated that InPEC isolates from different pathotypes were highly heterogeneous whereas those of the same pathotype were extremely similar. Plasmid analysis revealed that K88 and/or est/elt were found on pGX18-2-like/pGX203-2-like and pGX203-1-like IncFII plasmids, while F18 and elt/est, as well as diverse ARGs were found to co-locate on IncFII/IncFIB plasmids with a non-typical backbone. Moreover, these key virulence genes were flanked by or adjacent to IS elements. Our findings indicated that both clonal expansion and horizontal spread of epidemic IncFII plasmids contributed to the prevalence of InPEC and the specific virulence genes (F4, F18, elt and est) in the tested swine farms.
肠致病性大肠杆菌（InPEC）是引起农场动物细菌性腹泻的最常见原因之一，包括新生仔猪大量腹泻和断奶后腹泻（PWD）。在这项研究中，我们调查了中国南方 15 个猪场的 543 份非重复大肠杆菌分离株中 InPEC 的流行情况和相关的主要毒力因子。在 69 株（12.71%）大肠杆菌分离株中发现了与 InPEC 相关的 6 个主要毒力基因，包括 est（6.62%）、K88（4.79%）、elt（3.68%）、eae（1.47%）、stx2（0.92%）和 F18（0.55%）。鉴定出 3 种 InPEC 病原型，包括 ETEC（8.10%）、EPEC（1.29%）和 STEC/ETEC（0.92%）。特别是，K88 仅在繁殖场的 ETEC 中发现，而 F18 仅存在于育肥场的 STEC/ETEC 混合株中。对 37 株大肠杆菌分离株的全基因组序列分析表明，InPEC 菌株经常携带多种抗生素耐药基因（ARG）。est、elt 和 F18 也被发现与单个 IncFIB/IncFII 质粒上的 ARG 共存。不同病原型的 InPEC 分离株也具有不同的毒力基因和抗菌药物耐药基因谱。种群结构分析表明，不同病原型的 InPEC 分离株高度异质，而同一病原型的分离株则极为相似。质粒分析表明，K88 和/或 est/elt 位于 pGX18-2-like/pGX203-2-like 和 pGX203-1-like IncFII 质粒上，而 F18 和 elt/est 以及多种 ARG 则位于具有非典型骨架的 IncFII/IncFIB 质粒上。此外，这些关键毒力基因被 IS 元件包围或毗邻。我们的研究结果表明，克隆扩张和流行的 IncFII 质粒的水平传播共同导致了测试猪场中 InPEC 和特定毒力基因（F4、F18、elt 和 est）的流行。
