Virulence and fitness gene patterns of Shiga toxin-encoding Escherichia coli isolated from pigs with edema disease or diarrhea in Germany

Fecal Escherichia coli isolates (n = 3,218) from piglets with edema disease or diarrhea were screened for the genes of Stx2 and Stx2 variants. A total of 283 E coli isolates (8.8 %) proved exclusively positive for Stx2e and most of these (85.1 %) harbored genes for F18 fimbria. No recognized adhesins were detectable in 14.5 % of the isolates. Genes for heat-stable or heat-labile E.coli enterotoxins were found in F18(+) as well as F18(-) isolates (51.9 % and 33.3 %, respectively). Five isolates also harbored fyuA and irp2 genes which are indicative of a high pathogenicity island in E coli. All Stx2e, isolates lacked genes for intimin, EHEC hemolysin, STEC autoagglutinating adhesin, subtilase cytotoxin, serine protease EspI. The majority of Stx2e, isolates belonged to phylogenetic groups A (59.3 %) and D (38.9 %) and only few isolates were classified as 31 and B2 (1.8 %). The results suggest that Stx2e-producing E coli strains are highly prevalent in diseased pigs in Germany. Despite their significant diversity, most strains possess all typical features (Stx2e, F18) of porcine edema disease E coli. However, a considerable portion of porcine strains resembles published human Stx2e(+) strains in that they lack any recognized pig-associated adhesin. Thus, a zoonotic potential cannot be excluded for these strains.