Bacteria and the mucus blanket in experimental small bowel bacterial overgrowth

Self-filling blind loops were created experimentally in jejunal segments of specific pathogen-free male Wistar rats, and the loop contents and mucosa were examined over an 8-week period for evaluation of the interaction between mucus and luminal bacteria. Corresponding jejunal segments from rats that did not undergo surgery were used as controls. Proliferation of anaerobic bacteria developed in the test animals by the first week after surgery. Despite anaerobic bacterial proliferation, no adherence by bacteria to the intestinal microvillus surface was observed by scanning or transmission electron microscopy. Rather, bacteria were present within the mucus layer overlying the intestinal mucosal surface. Immunoassay of goblet cell mucin demonstrated an increase in the proportion of mucin present in the intestinal lumen and a decrease in mucin levels in the jejunal mucosa. These results suggest that the interaction of bacteria with mucus is an important mechanism of protection of the mucosal surface in experimental small bowel bacterial overgrowth.