Bacterial overgrowth and mucosal changes in isolated (Thirty-Vella) ileal loops in rabbits. Effects of intraluminal antibiotics.

Atrophy of villi, with increases in crypt depth and Paneth cell number and size, occurs in chronically isolated (Thirty-Vella) ileal loops in rabbits. These loops are known to be heavily colonized with aerobic bacteria. To study the possible effect of the bacterial overgrowth, 2 experiments were performed. In the first study, two isolated ileal loops were created in each of 14 rabbits. The antibiotic loop was flushed with nonabsorbable antibiotics (neomycin, bacitracin, and gentamycin), whereas the control loop was flushed with saline. The antibiotic solution achieved a reduction in bacterial growth as compared to the loops flushed with saline. In the second study, a single ileal loop was created in each of 20 rabbits. Loops of 11 animals were flushed with an absorbable antibiotic (cefoxitin) and gentamycin, whereas those in 9 other rabbits were flushed with saline. This antibiotic combination achieved an essentially sterile loop. In both experiments, the Paneth cell population and crypt depth were less in antibiotic loops as compared to saline loops, whereas the degree of villus atrophy was nearly equal. These studies suggest a link between the overgrowth of bacteria seen in these isolated loops and the morphologic changes in the crypts.