Pathogenic potential and virulence genotypes of intestinal and faecal isolates of porcine post-weaning enteropathogenic Escherichia coli

This present study investigates differences in pathogenic potential and virulence genotypes of intestinal and faecal isolates of EPEC from newly-weaned pigs. For this we inoculated ligated ileal loops of four weeks old weaned pigs to assess EPEC adherence to enterocytes by histology and immunohistology. Virulence gene patterns were identified by using a PCR-microarray. Intestinal EPEC isolates of sero −/intimin types O45:H11:eae-β, O49:NM:eae-β, O84:H7:eae-γ, and O123:H11:eae-β formed adherent microcolonies of EPEC with AE lesions on ileal villi more frequently than faecal isolates of O28:H28:eae-NT, O108:H9:eae-β, O145:H28:eae-γ and O157:H2:eae-β (p ≤ 0.05). The PCR-array analysis of both groups detected all together 25 virulence genes of LEE (Locus of Enterocyte Effacement), and of non-LEE pathogenicity islands, of plasmids and phages characteristic to EPEC. Intestinal isolates carried significantly more virulence genes than faecal isolates (p ≤ 0.05). Intestinal isolates possessed efa1, lpfA, and tsh genes most likely contributing to enterocyte adhesion while faecal isolates did not carry these genes (p ≤ 0.05). Overall, the ileal loop model in weaned pigs combined with virulence genotyping PCR-array indicated a greater pathogenic potential of intestinal isolates over faecal isolates of porcine post-weaning EPEC. Differing virulence genotypes of the intestinal and faecal isolates as demonstrated here suggests dynamic evolutionary events within the population of porcine EPEC.