Abstract
BackgroundSwine extraintestinal pathogenic Escherichia coli (ExPEC) is an important pathogen that leads to economic and welfare costs in the swine industry worldwide, and is occurring with increasing frequency in China. By far, various virulence factors have been recognized in ExPEC. Here, we investigated the virulence genotypes and clonal structure of collected strains to improve the knowledge of phylogenetic traits of porcine ExPECs in China.ResultsWe isolated 64 Chinese porcine ExPEC strains from 2013 to 14 in China. By multiplex PCR, the distribution of isolates belonging to phylogenetic groups B1, B2, A and D was 9.4%, 10.9%, 57.8% and 21.9%, respectively. Nineteen virulence-related genes were detected by PCR assay; ompA, fimH, vat, traT and iutA were highly prevalent. Virulence-related genes were remarkably more prevalent in group B2 than in groups A, B1 and D; notably, usp, cnf1, hlyD, papA and ibeA were only found in group B2 strains. Genotyping analysis was performed and four clusters of strains (named I to IV) were identified. Cluster IV contained all isolates from group B2 and Cluster IV isolates had the strongest pathogenicity in a mouse infection model. As phylogenetic group B2 and D ExPEC isolates are generally considered virulent, multilocus sequence typing (MLST) analysis was performed for these isolates to further investigate genetic relationships. Two novel sequence types, ST5170 and ST5171, were discovered. Among the nine clonal complexes identified among our group B2 and D isolates, CC12 and CC95 have been indicated to have high zoonotic pathogenicity. The distinction between group B2 and non-B2 isolates in virulence and genotype accorded with MLST analysis.ConclusionThis study reveals significant genetic diversity among ExPEC isolates and helps us to better understand their pathogenesis. Importantly, our data suggest group B2 (Cluster IV) strains have the highest risk of causing animal disease and illustrate the correlation between genotype and virulence.
Highlights
Swine extraintestinal pathogenic Escherichia coli (ExPEC) is an important pathogen that leads to economic and welfare costs in the swine industry worldwide, and is occurring with increasing frequency in China
Based on the isolation site, ExPEC can be classified as uropathogenic E. coli (UPEC), avian pathogenic E. coli (APEC), newborn meningitis E. coli (NMEC) or sepsis E. coli (SEPEC)
In this study, a total of 19 VR genes in 64 Chinese porcine ExPEC strains were detected by PCR
Summary
Swine extraintestinal pathogenic Escherichia coli (ExPEC) is an important pathogen that leads to economic and welfare costs in the swine industry worldwide, and is occurring with increasing frequency in China. Various virulence factors have been recognized in ExPEC. Extraintestinal pathogenic Escherichia coli (ExPEC) is a major pathogenic agent causing disease worldwide. It can lead to many kinds of extraintestinal diseases, including newborn meningitis, sepsis, and urinary tract disease [1]. ExPEC can be distinguished from intestinal pathogenic E. coli and commensal E. coli by isolation site and genetic patterns [4]. Based on the isolation site, ExPEC can be classified as uropathogenic E. coli (UPEC), avian pathogenic E. coli (APEC), newborn meningitis E. coli (NMEC) or sepsis E. coli (SEPEC). The infectivity of ExPEC involves various extraintestinal virulenceassociated factors in microbe-host interactions, rather than a simple mechanism [5]. Genome plasticity of ExPEC is the basis for rapid adaptation to the changing environment, which in turn increases the diversity of E. coli populations
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