Distribution of K88 Escherichia coli-adhesive and nonadhesive phenotypes among pigs of four breeds.

Enterotoxigenic Escherichia coli expressing K88 fimbrial adhesins often cause diarrhea in young pigs. However, some pigs are inherently resistant to colibacillosis, because they lack receptors on their epithelial cell brush borders to which the fimbriae bind. Phenotypic diversity with respect to the binding of E. coli expressing K88 of the three variant types (K88ab, K88ac, and K88ad) was reported by Bijlsma et al. (1982), and binding specificities for each phenotype were described: A (adhesive to all three variants), B (adhesive to K88ab and K88ac), C (adhesive to K88ab and K88ad), D (adhesive to K88ad) and E (nonadhesive). Because brush border adhesiveness has been correlated with disease susceptibility, swine K88 adhesive phenotypes are of significance in the control of enteric disease. To determine the prevalence of the various K88 adhesive phenotypes in the swine population in the Midwestern United States, we tested epithelial cell brush borders of 24 purebred pigs from each of four breeds (Chester White, Duroc, Hampshire and Yorkshire) for adhesiveness to each of the K88 variants. Four, 4-week-old pigs (the largest and smallest healthy female littermates from two litters) were collected from each of 24 farms. Brush border vesicles from the pigs were tested for ability to bind E. coli expressing each K88 variant. The five brush border adherence patterns described for phenotypes A-E were observed. In addition, brush borders from some pigs only bound K88ab + bacteria. Nearly three quarters of the pigs whose brush borders tested, were found to be phenotype A (43%) or phenotype E (28%). These were the most common phenotypes in each breed, except Hampshire, in which case phenotypes C (17%) and D (25%) were more common than E (8%). There appeared to be no relationship between the phenotype of a pig and its weight relative to its littermate.