Occurrence of K99 antigen on Escherichia coli isolated from pigs and colonization of pig ileum by K99+ enterotoxigenic E. coli from calves and pigs

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Abstract
Several strains of enterotoxigenic E. coli (ETEC) isolated from pigs had an antigenic (K99) previously reported only on strains of calf and lamb origin which facilitates intestinal colonization in the latter 2 spp. Several human ETEC were also tested for K99; however, none were positive. Each of four K99-positive ETEC strains of calf origin and 1 of pig origin produced K99 in pig ileum in vivo, adhered to villous epithelium in pig ileum, colonized pig ileum and caused profuse diarrhea in newborn pigs. In contrast to the K99-positive strains above, four K99-negative ETEC from humans and chickens and one K99-positive ETEC from a calf did not colonize pig ileum or did so inconsistently. When the K99-negative strains did colonize, they had little or no tendency to adhere to intestinal villi. K99 apparently facilitates adhesion to and colonization of pig ileum by some ETEC.