Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology


A ligated intestinal loop model was used to evaluate the ability of enterocytes to support adherence of K88+ bacteria in different regions of the intestine, and different ages of pigs. Wild-type K88+ enterotoxigenic Escherichia coli (ETEC) and a non-pathogenic K88- E. coli strain were injected into ilea! and jejunal loops of pigs ranging from 1 to 8 weeks of age, and allowed to incubate for 8 hours. Thereafter, loops were collected for histologic analysis, and to assess bacterial concentration. There was no significant difference in concentration of bacteria per gram of washed intestine in the ileal or jejunal loops, or between the wild-type strain and the negative control. However, the number of bacteria adherent to intestinal epithelia, determined by blind histologic scoring, was affected both by intestinal location and animal's age. Heal and jejunal loops of 1-week old pigs showed confluent bacterial adherence from the base to the tip of villi. The amount of K88+ ETEC adherent to epithelium in jejunal loops of pigs 2 weeks old and older was not significantly greater than that in loops inoculated with the non-pathogenic control. Presence of adherent ETEC in ileal loops also decreased as pigs aged, and was similar to that of the non-pathogenic control strain by 5 weeks of age. The results of this study suggest that pigs become increasingly resistant to K88.,. ETEC colonization as they become older, with complete resistance occurring by about 5 weeks of age. They further suggest that resistance is not a function of receptor loss. We hypothesize that resistance to K88-mediated disease is a function of changes in epithelial cell covering (mucus and/or glycocalyx), which changes qualitatively and quantitatively as animals age. We suggest that the epithelial cell covering provides a mechanical barrier that limits the access of bacteria to epithelial cell-associated receptors, thus it prevents colonization.

Library of Congress Subject Headings

Escherichia coli infections in swine Intestines -- Infections Epithelial cells Natural immunity



Number of Pages



South Dakota State University