VIRULENCE PROPERTIES OF ESCHERICHIA-COLI STRAINS ISOLATED FROM PATIENTS WITH INFLAMMATORY BOWEL-DISEASE

Escherichia coli strains cultured from 74 patients with inflammatory bowel disease at different stages of disease activity (Crohn's disease (40), ulcerative colitis (34)) and 18 healthy controls were studied in relation to haemolysin and verotoxin production and enteroadherence. Disease activity was assessed by standard clinical and laboratory tests. Haemolytic E coli were isolated from 18% of patients with Crohn's disease, 24% with ulcerative colitis, and 11% of healthy controls. None of these differences was significant. No verotoxin producing strains were detected among the 216 E coli isolates examined but the extract from five strains (Crohn's (4), ulcerative colitis (1) produced a distinctive cytopathic effort on Vero cell monolayers which was later shown not to be due to verotoxin. The adhesion indices of E coli isolates cultured were: mean (SEM) 42.2 (6.4) for Crohn's disease, 43.3 (6.2) for ulcerative colitis, and 11.3 (2.0) for normal controls (p less-than-or-equal-to 0.0001). Adhesive E coli were isolated from 62% of patients with Crohn's disease and 68% with ulcerative colitis but from only 6% of normal controls (p less-than-or-equal-to 0.0002). Neither haemolysin production nor enteroadherence was dependent upon disease activity, disease location, sulphasalazine treatment, or previous intestinal resection. These results indicate that only enteroadherent E coli were frequently associated with inflammatory bowel disease; their relation to the pathogenesis of these conditions, however, remains uncertain.