Models for studying the adhesion of enterobacteria to the mucosa of the human intestinal tract

Adhesive Escherichia coli in inflammatory bowel disease and infective diarrhoea

The clinical features of ulcerative colitis and Crohn's disease are similar to those of infections of the bowel, although their cause is uncertain. Many bacteria that cause intestinal diseases adhere to the gut mucosa, and adhesion of pathogenic Escherichia coli is resistant to D-mannose. The adhesive properties of isolates of E coli were assessed by assay of adhesion to buccal epithelial cells with mannose added. The isolates were obtained from patients with inflammatory bowel diseases (50 with a relapse of ulcerative colitis, nine with ulcerative colitis in remission, 13 with Crohn's disease, and 11 with infectious diarrhoea not due to E coli) and 22 controls. The median index of adhesion to buccal epithelial cells (the proportion of cells with more than 50 adherent bacteria) for E coli from patients with ulcerative colitis in relapse was significantly higher (43%) than that for controls (5%) and patients with infectious diarrhoea (14%). The index was not significantly different among isolates from patients with ulcerative colitis in relapse, Crohn's disease (53%), and ulcerative colitis in remission (30%). If an index of adhesion of greater than 25% is taken as indicating an adhesive strain 86% of isolates of E coli from patients with inflammatory bowel disease were adhesive compared with 27% from patients with infective diarrhoea and none from controls. The adhesive properties of the isolates from patients with inflammatory bowel disease were similar to those of pathogenic intestinal E coli, raising the possibility that they may have a role in the pathogenesis of the condition; the smaller proportion of adhesive isolates in patients with infective diarrhoea due to other bacteria suggests that the organism may be of primary importance rather than arising secondarily.

HeLa cell and buccal epithelial cell adhesion assays for detecting intestinal Escherichia coli with adhesive properties in ulcerative colitis

The two methods used to detect intestinal Escherichia coli in patients with ulcerative colitis, HeLa cell and buccal epithelial cell (BEC) adhesion assays, were compared. Both methods showed a significant difference between the adhesive property of colitic and control E coli: p less than 0.0002 and p less than 0.01 for the buccal epithelial cell and HeLa cell methods, respectively. HeLa cells did not detect all BEC positive isolates which were quantitatively more adhesive than any control isolate. All BEC negative isolates were HeLa cell negative. The BEC technique seems to be more sensitive for detecting adhesive E coli in ulcerative colitis because the true incidence of adhesive E coli in ulcerative colitis was higher than that determined by the HeLa cell method.

Ulcerative colitis and Escherichia coli with adhesive properties

A quantitative assessment of the mannose resistant, adhesive property of Escherichia coli from patients with ulcerative colitis and from controls was made using a buccal epithelial cell adhesion assay, which also permitted assessment of adhesion to cells from other host sources. E coli from patients with ulcerative colitis adhered to buccal epithelial cells to a greater extent than those obtained from controls (p less than 0.0001), but did not show an increased affinity for the buccal epithelial cell of their host, compared with those obtained from other sources. The mannose resistant adhesive property of E coli raises the possibility that it has a role in the pathogenesis of ulcerative colitis.

In vitro adhesion of enterotoxigenic Escherichia coli to human intestinal epithelial cells from mucosal biopsies

An adhesion assay with isolated human enterocytes prepared from duodenal biopsies has been developed and tested by using human enterotoxigenic Escherichia coli expressing colonization factor antigens I and II (CFA/I and CFA/II) and type 1 fimbriae. Enterotoxigenic E. coli strains H10407 (CFA/I) and B2C (CFA/II) bound to duodenal enterocytes to a much greater extent (mean of 4.6 and 4.0 bacteria per brush border) than did strain H10407P, a CFA/I- mutant of H10407 (mean of 0.1 bacteria per brush border). Type 1 fimbriae also promoted adhesion of strain H10407P to duodenal enterocytes but attachment was to basolateral rather than brush border surfaces. CFA/I and CFA/II, on the other hand, promoted adhesion only to human enterocyte brush borders.