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Adhesion of Escherichia coli in piglets and association of phenotypes to known candidate genes in South African breeds
Enterotoxigenic Escherichia coli is a major pathogenic bacterium that causes diarrhoea in pre-weaned and post-weaned piglets. The adhesion of E. coli to the brush borders of the epithelial cells of piglets is a prerequisite for effective colonisation leading to diarrhoea. Successful adhesion occurs in the presence of the E. coli receptors that are found on the brush borders of the epithelial cells. The objective of the study was to compare the susceptibility of South African breeds to enterotoxigenic E. coli strains. An in vitro adhesion experiment was carried out for F4, PAA and EAST-1 E. coli strains using intestinal brush borders from 109 pigs of three South African pig breeds. Large White, indigenous and crossbred pigs that were 3-12 weeks old were used. The results showed significant differences (P <0.05) in adhesion frequencies of receptors among the three breeds. Adhesion phenotypes, adhesive, weakly adhesive and non-adhesive were found in all breeds. The F4 and PAA strains adhered in all three breeds. The Indigenous pigs had the highest frequency of non-adhesive intestines and over 70 % of the Large White pigs were adhesive to all strains. In indigenous and crossbred pig's adhesion was higher in suckling piglets than in weaners. The TFRC, MUC13, MUC4 and MUC20 genotypes were not associated with adhesion phenotypes. The South African population studied carried receptors for all strains measured. If there is an outbreak of E. coli carrying the above strains, the South African population is most likely to be affected. The indigenous pigs of the South African population studied were more resistant to F4, PAA and EAST-1 E. colistrains compared to Large White and crossbred pigs.
Keywords: E. coli strains, piglets, adhesion, susceptibility