Enteric Colibacillosis in Gnotobiotic Swine: An Electron Microscopic Study

SUMMARY The ultrastructural changes in the ileal absorptive cells of gnotobiotic pigs infected with Escherichia coli O138:K81:NM were studied. The initial ultrastructural changes, present at 8 hours after pigs were exposed to E. coli , were decrease in pinocytotic vesicles, dilatation of the intercellular spaces, and accumulation of fat in the cytoplasm. As the infection progressed, an increased number of cells had regressive changes identical to the degenerative changes present in cells of the germfree controls undergoing necrobiosis. There was no evidence of attachment between the bacteria and the microvilli, and presence of the bacteria in direct contact with the brush border did not visibly damage the microvilli. The bacteria seemed to enter the cells separately and were always free within the cytoplasm. Bacteria were found only in cells with evidence of regressive changes.