Bacterial load in animal models of acute and chronic 'reactivated' colitis

BACKGROUND: The involvement of enteropathogenic microorganisms in the pathogenesis of inflammatory bowel disease (IBD) and their importance in the different phases of inflammation are still unknown. AIM: To quantify the aerobic bacterial load in models of acute and chronic 'reactivated' colitis, and correlate this with damage. METHODS: Acute colitis was induced in rats by administration of trinitrobenzene sulfonic acid (TNBS) or dextran sulfate sodium (DSS). Colitis was 'reactivated' 6 weeks later by intravenous administration of TNBS. The distal colon was removed and scored macroscopically before inoculating samples. RESULTS: Bacterial load in rats with acute colitis (72 h) and chronic 'reactivated' colitis or their controls was significantly higher than untreated (p < 0.05); however, there were significantly more bacteria in acute colitis than in chronic 'reactivated' or their controls (p < 0.05). Both acute and chronic 'reactivated' colitis had significantly higher damage scores than untreated animals (p < 0.05). Bacterial load and damage score were significantly correlated only with acute colitis. CONCLUSIONS: The role of enteric microflora in the pathogenesis of IBD is greater during the acute phase of colitis. The correlation between bacterial load and tissue damage suggests that damage contributes to bacterial multiplication and exacerbation of colitis. Normal colonic flora may contribute to the relapse of the disease.