Bacterial colonization and morphology of the intestine in porcine Escherichia coli enterotoxemia (edema disease).

Twenty-one pigs were divided into three groups. Pigs in one group were inoculated with the intestinal contents which included bacteria from a pig with edema disease. Pigs in another group were inoculated with a culture of Escherichia coli serogroup O 139:K12(B):H1 isolated from the aforementioned contents, and pigs in a third group served as uninoculated controls. The infection was similar following both inocula. Enterotoxemia developed in 11 of the 14 pigs allowed to survive for more than two days. The onset varied from two to seven days after inoculation. There were maximal viable counts of E. coli in the intestine from the second day post-inoculation and thereafter. In frozen and paraffin sections, as well as by scanning electron microscopy, the organisms were seen on the surface of the small intestinal epithelium where they formed either isolated colonies or continuous layers. They colonized the lower small intestine more intensely than the upper section. The intestinal epithelium and the villi of infected pigs were indistinguishable morphologically from the tissues of three uninoculated control pigs. The diarrhea which was observed in controls and inoculated pigs before inoculation and the villus atrophy in controls and inoculated pigs indicated a preexisting infection with at least one other agent.