Frequency of Diarrheagenic Virulence Genes and Characteristics in Escherichia coli Isolates from Pigs with Diarrhea in China.

Gui-Yan Yang,Yao-Hong Zhu,Lian-Guo Jiao,Jiu-Feng Wang,Jin-Hui Su,Liang Guo

doi:10.3390/microorganisms7090308

Abstract

Intestinal pathogenic Escherichia coli (InPEC) is a leading cause of postweaning diarrhea (PWD) in pigs. Here, a total of 455 E. coli strains were isolated from small intestinal content or feces from pigs with PWD in 56 large-scale (>500 sows; 10,000 animals per year) swine farms between 2014 and 2016. The frequency of occurrence of selected virulence factors for InPEC pathotypes was detected in 455 isolates by real-time PCR. Sequence types (STs), pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility profiles of 171 E. coli isolates from 56 swine farms were further determined. The heat-labile enterotoxin (LT) was the most common (61.76%), followed by heat-stable enterotoxin (STb) (33.19%), stx2e (21.54%), STa (15.00%), eae (8.98%), cnf2 (5.71%), stx2 (5.71%), F18 (3.25%), and F4 (2.25%) with rates varying by geographic area and year of isolation. Notably, hybrids of E. coli isolates were potentially more virulent, as some InPEC hybrids (virotype F18:LT:eae:stx2e) can rapidly cause cell death in vitro. Genotypic analysis revealed that the most prominent genotype was ST10 (12.87%). The PFGE patterns were heterogeneous but were not ST or virotype related. A total of 94.15% of isolates were multidrug-resistant, with average resistance rates ranging from 90.05% for nalidixic acid to 2.34% for meropenem. Our investigation contributes to establishing the etiology of diarrhea and developing intervention strategies against E. coli-associated diarrheal disease in the future.

Highlights

Pathogenic Escherichia coli is one of the most important causes of postweaning diarrhea (PWD) in pigs, and the high associated mortality is responsible for significant economic losses [1]
The aim of this study was to investigate the proportion of selected virulence factors and antimicrobial resistance in E. coli isolates from pigs with PWD in Chinese large-scale (>500 sows; 10,000 animals per year) swine farms, and examine the genetic relatedness of these specific pathotypes to better understand the geographic dissemination of diarrheagenic E. coli in pigs
In contrast to a previous report where only 6% (13/215) of the postweaning E. coli strains possessed the genes of stx2e [23], we found 21.54% (98/455) of the E. coli isolates were stx2e-positive from pigs with PWD

Summary

Introduction

Pathogenic Escherichia coli is one of the most important causes of postweaning diarrhea (PWD) in pigs, and the high associated mortality is responsible for significant economic losses [1]. Intestinal pathogenic E. coli (InPEC) strains in pigs include enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), and Shiga toxin-producing E. coli (STEC; known as verocytotoxigenic E. coli (VETC)) [1]. Human and animal pathogenic E. coli strains share a common genetic background, and diseases caused by each pathotype involve specific colonization and virulence factors [3]. The EPEC strains are defined as the locus of enterocyte effacement (LEE) pathogenicity island and eae–harboring diarrheagenic E. coli that can form attaching and effacing (A/E) lesions on intestinal cells but do not possess the stx gene [2]. STEC with the genetic variant stx2e possess the ability to cause edema disease (ED) [6]

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