"DEscriptION OF THE PREFERRED EMBODIMENTS
 Fusobacterium varium is a bacterium belonging to the genus Fusobacterium of the family Bacteroidaceae and was detected from the mucosa of a patient with ulcerative colitis at the active phase by bacterial cell culture and immunostaining. The rates of these detections were significantly higher than those observed for patients with ulcerative colitis at the remission stage, Crohn's disease, ischemic colitis, and colomic adenoma. Therefore, this bacterium is considered to be a causal bacterium or an exacerbation factor. From such information, it would be concluded that the patients with ulcerative colitis could be cured by administering a drug selectively killing this bacterium or an antimicrobial agent to remove the bacterial cells from the mucosa in the lesions. More specifically, there can be used antimicrobial agents having high susceptibility to Fusobacterium varium, such as tetracycline, penicillin, MNZ, imipenem, amoxicillin, cefmetazole, ampicillin, fosfomycin and chloramphenicol.
 It has been recognized that the toxins produced by Fusobacterium varium cells have toxicity to vero cells. Therefore, the toxins were analyzed and it was found that they were organic acids produced by Fusobacterium varium and that the principal component thereof was identified to be butyric acid. Thus, when butyric acid was injected into the rectum of a mouse, a lesion similar to ulcerative colitis was induced. Accordingly, if administering a drug, which can neutralize and/or adsorb the butyric acid to a patient, the development of any lesion may be prevented or such conditions may be treated. Specifically, an agent for adsorbing organic acids such as activated carbon can be employed.
 Since Fusobacterium varium cells are adhered to the surface mucosa of active ulcerative colitis, the crisis of ulcerative colitis can be prevented by inhibiting the adhesion of Fusobacterium varium cells to the affected mucosa even if Fusobacterium varium cells are present in the intestinal flora. Specifically, a drug for protecting mucosa such as sucralfate and ecabe sodium can be used.
 As an evidence that Fusobacterium varium cells invade from digestive tracts into the intestinal mucosa, an antibody (serum antibody) against Fusobacterium varium is detected in the sera of the patients with ulcerative colitis in a high detection rate and high antibody titers by the ELISA assay. There has recently been elucidated the invasion mechanism of various kinds of bacteria into mucosa. Bacteria act on the mucosal cells by themselves to thus make the cells produce receptors and then they invade into the cells. Fusobacterium varium cells may possess the same function. Moreover, it would be considered that if Fusobacterium varium cells invade into the mucosa, macrophages can be activated and they may be involved in the crisis and exacerbation of inflammation. Therefore, the inflammation can be controlled by blocking the process of the bacterial invasion into the mucosa."