Development of an ex vivo model for investigating the bacterial association to the gut epithelium of pigs.

To study enterotoxigenic Escherichia coli (ETEC) association to the gut of pigs, a simple and reproducible experimental model would be helpful. The aim of this experiment was to establish a model for studying the association of ETEC to the gut epithelium of pigs. Intestinal segments were prepared from 4 weaned pigs, which were tested susceptible to E. coli O149:F4 (homo- and heterozygotic; 2 pigs each) and O138:F18 (all homozygotic). Five segments were taken from 50% of the intestinal length measured from duodenum [mid small intestine (SI)], and 5 segments were taken from 90% distal to the duodenum (distal SI). The segments were immersed in Dulbecco's Modified Eagle Medium (DMEM) and kept on ice. Polyethylene tubing was inserted into either end of the segment and tied. The tissue was washed with 50 mL of PBS. The other end of segment was tied, 10 mL of DMEM alone or DMEM containing either E. coli F4 or F18 was inoculated, and the segment was sealed with Teflon plug. The segment was immersed in DMEM in a 300-mL infusion bottle in a shaking water bath at 37°C. After 1 h the segment was removed, tissue was washed with 50 mL of PBS, weighed, and homogenized in PBS. Final dilution of 10(-6) was prepared from the content and homogenate. The E. coli was enumerated on MacConkey agar. Data were analyzed according to a 2 × 3 × 2 parametric model including the effects of intestinal segment, E. coli strain, and site of SI with GLM procedure in SAS. A t-test was used to analyze the effect of genotype in F4-inoculated segment. The binding of E. coli on the tissue was 10 times higher (P < 0.001) for F4 than F18. The E. coli F18 was highest (P < 0.05) in mid SI whereas differences were not observed (P > 0.05) between sites of SI for F4. Fewer (P < 0.001) bacteria bound in the control and they associated more (P = 0.10) at distal than mid SI. The E. coli did not differ (P > 0.05) between genotypes in F4-inoculated segment. In conclusion, the ex vivo model may be feasible to investigate the ETEC association to the gut epithelium of pigs.