Bacteriological studies of experimental ulcerative colitis

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Abstract
The carrageenan model for ulcerative colitis has been studied in an effort to define the role of bacteria in the experimental disease. It was found that guinea pigs given a 5% w/v carrageenan solution developed cecal ulcerations within 14 days which were histologically similar to lesions seen in the human disease. Bacteriological studies of the cecal contents of carrageenan recipients indicated that both the coliform and gram negative anaerobic bacterial counts were increased as compared to bacterial counts obtained from healthy control animals. Suppression of cecal bacterial populations with oral antimicrobial agents during carrageenan challenge was used to determine whether specific microflora populations were necessary for ulceration. It was found that antimicrobials active versus obligate anaerobes prevented cecal ulceration in carrageenan recipients, while antimicrobials active versus gram positive organisms or coliforms did not suppress ulcer development. It was also noted that germ-free animals given carrageenan did not develop typical lesions, but germ-free animals associated with a conventional microflora acquired cecal ulcerations during carrageenan challenge. These results suggest that bacteria are an important factor in the development of experimental ulcerative colitis. Recent experiments indicate that a cytotoxic substance is present in sera and stool of ulcerative colitis patients and guinea pigs, but not in sera or stool from patients with other inflammatory bowel diseases. These data may provide a link between the experimentally-induced disease and ulcerative colitis as seen in humans.