Virulence genes of pathogenic Escherichia coli from ill pigs in China and their relationship with O-serogroups

Abstract:

[Objective] We determined the distribution of serogroups and virulence factors among Escherichia coli isolates from pigs with diarrhea and/or edema disease from 10 provinces in China between 1998 and 2007. [Methods] Three hundred E. coli isolates were serogrouped with O-antisera and detected for genes of enterotoxins, shiga-toxin-two-variant (Stx2e), intimin, K88, K99, 987P, F18 and F41 fimbrial antigens by PCR. [Results] Among 300 isolates, 233 were determined to be placed in serogroups, 50 were unable to be serogrouped, and the rest 17 auto-agglutinated. These isolates distributed in 45 serogroups and 57.1% (133/233) belonged to 5 O serogroups: O149, O107, O139, O93 and O91. Several uncommon O serogroups were discovered. PCR analysis confirmed the genes of estⅠ(STa), estⅡ(STb), elt (LT), stx2e (Stx2e) and eaeA (Intimin) within the isolates. There were six pathotypes of porcine E. coli by their pathogenic factors, namely enterotoxigenic E. coli (ETEC), shiga toxin-producing E. coli (STEC), attaching-effacing E. coli (AEEC), ETEC/ STEC, AEEC/ETEC and AEEC/ETEC/STEC. The correlation between pathotypes and serogroups showed that the combinations of O149/K88/estⅡ, O149/K88/estⅡ+elt, O107/F18/estⅡ, O93/estⅡand O98/estⅡwere common types in ETEC strains, O139/ F18/stx2e for STEC strains, eaeA gene for AEEC strains, O107/F18/estI+stx2e, O107/F18/estⅡ+ stx2e and O116/F18/estⅠ+elt+stx2e for ETEC/STEC strains, O91/estⅠ/eaeA and O107/estⅠ/eaeA for AEEC/ETEC/STEC strains.”[Conclusion] ETEC was commonly associated with swine colibacillosis, whereas the kinds of enteric E. coli pathogens become more complex in China.