The Microbial Flora of the Rectal Mucosa and Faeces of Patients with Crohn's Disease Before and During Antimicrobial Chemotherapy

Abstract

The fecal flora and mucosa-associated flora (MAF) of rectal biopsy material from 12 patients with active Crohn''s disease were studied before and during treatment with a combination of metronidazole and cotrimoxazole given orally for at least 2 wk. The total fecal flora was greater than the MAF although the proportions of bacterial groups were similar. The changes observed during treatment included obligate anaerobes such as Bacteroides spp. decreased in feces (P < 0.05) and in MAF (P < 0.02); the total count of facultative bacteria increased in the feces (P < 0.002) but not in the MAF. Steptococci, predominantly enterococci, increased significantly in feces (P < 0.001) and in MAF (P < 0.02) such that they became predominant components of these florae. Facultative gram-negative bacilli were unaltered in feces but significantly reduced in the MAF (P < 0.05). Sporing clostridia were infrequently isolated from the MAF but were significantly reduced in the feces (P < 0.01). During the treatment period, 8 of the 12 patients showed clinical improvement, but this could not be related to the site or extent of disease or to specific changes in fecal flora or MAF. This combination of antibacterial agents causes profound alterations to the bacterial flora of mucosa and feces and these changes may help to define the role of bacteria in the pathogenesis of Crohn''s disease.