The role of the resident intestinal flora in acute and chronic dextran sulfate sodium-induced colitis in mice

Objective There is increasing evidence that the intestinal microflora plays an important role in the pathogenesis of inflammatory bowel disease. In the present study, we examined the role of the resident intestinal flora in our model of dextran sulfate sodium (DSS)-induced acute and chronic colitis in mice. Methods Acute colitis was induced in BALB/c mice with 5% DSS in their drinking water for 7 days. Chronic colitis was established after four cycles of feeding 5% DSS for 7 days and water for 10 days. For eliminating intestinal bacteria, mice were injected intraperitoneally with metronidazole end ciprofloxacin. We analysed four parameters: (1) body weight, (2) length of the colon, (3) histological score, and (4) myeloperoxidase activity. Results In acute DSS colitis treatment with antibiotics led to an improvement of the histological parameters (epithelial damage, P< 0.05; inflammatory infiltrate, P< 0.05) and colon length (P< 0.0028). A significant reduction in granulocyte infiltration was indicated by a 52.6% reduced myeloperoxidase activity in colonic biopsies. By contrast, in chronic colitis, treatment of mice with antibiotics failed to show significant effects. Conclusion In acute DSS-induced colitis bacteria and/or bacterial products play a major role in initiation of inflammation but not in chronic DSS colitis. Eur J Gastroenterol Hepatol 12:267-273 (C) 2000 Lippincott Williams & Wilkins.