The role of interdigestive small bowel motility in the regulation of gut microflora, bacterial overgrowth, and bacterial translocation in rats.

OBJECTIVE

To clarify the role of the migrating motor complex (MMC) in the regulation of small intestinal microflora and bacterial translocation.

SUMMARY BACKGROUND DATA

The intestinal microflora may serve as a source of infectious microorganisms. Failure of regulatory mechanisms of the intestinal flora could therefore play an important role in the pathogenesis of gut-derived infections.

METHODS

Rats were fitted with small intestinal myoelectrodes. MMCs were measured on a control day and 3 consecutive days during continuous administration of morphine or placebo. Mesenteric lymph nodes, liver, spleen, peripheral blood, duodenum, and ileum samples were cultured quantitatively.

RESULTS

The mean MMC cycle length in placebo-treated animals was 15.1+/-0.5 minutes. MMCs were completely disrupted after morphine treatment. Total bacterial growth in the duodenum was 7.27+/-0.34 10log colony-forming units (CFU)/g with placebo and 8.28+/-0.27 CFU/g with morphine. In placebo-treated animals, the mean MMC cycle length the day before culturing correlated with total bacterial growth in the duodenum. Translocation incidences to the mesenteric lymph nodes, liver, spleen, and blood were 0/8, 1/8, 0/8, and 0/8 with placebo and 7/8, 6/8, 5/8, and 0/8 with morphine. The overall translocation incidence was 1/8 in placebo-treated animals and 8/8 in morphine-treated animals.

CONCLUSIONS

The MMC is an important mechanism controlling bacterial growth in the upper small bowel. Its disruption with morphine promotes duodenal bacterial overgrowth and bacterial translocation.