The Effect of Metronidazole and Sulfasalazine on the Fecal Flora in Patients with Crohn's Disease

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Abstract
Twenty patients with Crohn's disease were treated with metronidazole (Flagyl®) or sulfasalazine (Salazopyrin®). Before and during treatment quantitative and qualitative studies of the aerobic and anaerobic fecal bacterial flora were performed. After 1 week of metronidazole and 1 month of sulfasalazine treatment the median value of the Bacteroides concentration decreased drastically. After 4 months the Bacteroides concentration was still low in patients receiving metronidazole but normalized in patients receiving sulfasalazine treatment. The number of patients in whom the concentration of different bacteria in stool specimens showed changes during treatment of more than one 10log of colony-forming units (cfu) per gram wet weight (i.e. more than 90%) was calculated. A comparison between pretreatment samples and those taken at the end of treatment showed a statistically significant decrease of Bacteroides species (P < 0.02) and a significant increase of fecal streptococci (P < 0.02) in patients treated with metronidazole but not in patients treated with sulfasalazine. The relevance of these findings and the role of the bowel microflora for the pathogenesis of Crohn's disease is discussed.