Detection of Fimbrial and Toxin Genes in Escherichia coli and their Prevalence in Piglets with Diarrhoea. The Application of Colony Hybridization Assay, Polymerase Chain Reaction and Phenotypic Assays

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Abstract
Two different genotypic methods, colony hybridization and polymerase chain reaction (PCR), were applied to detect enterotoxin, verotoxin and fimbrial genes in 708 Escherichia coli (E. coli) strains from piglets with diarrhoea. The results were compared with those obtained by phenotypic methods. DNA fragments specific for each of the enterotoxins LT, STa and STb, the verotoxins VT1, VT2 and VT2v, and for each of the fimbrial genes K88 (F4), K99 (F5), 987P (F6), F41 and F107, respectively, were used as probes in a colony hybridization assay of the E. coli strains. A PCR assay was used as genotypic test for the verotoxin gene. An Enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies was performed to test for the presence of K88 and K99 fimbriae, and a Vero cell test was performed to test for verotoxin production. Toxin detection kits were applied to detect the E. coli heat-labile enterotoxin (LT) and the heat-stable (STa) enterotoxin. The correlation between the results obtained by genotypic and phenotypic methods was 97.7-100%. The prevalence of the different fimbrial and toxin genes in E. coli strains from piglets with neonatal and postweaning diarrhoea were recorded. The verotoxin and the fimbrial F107 genes were found to be more frequent in postweaning E. coli strains than in neonatal E. coli strains.

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