Factors Contributing to the Efficacy of Fecal Microbiota Transplantation for Diarrhea-Dominant Functional Bowel Disorders.

Introduction: In cases of effective fecal microbiota transplantation (FMT) for irritable bowel syndrome (IBS), donor feces have been observed to be enriched in Bifidobacterium spp. Moreover, FMT for functional bowel disease can improve psychiatric symptoms. Although intestinal dysbiosis has received attention as one of the pathophysiologies of IBS, the efficacy of FMT for IBS has not yet been established. In this study, we performed a post hoc analysis of the efficacy of FMT, focusing on metabolites in donor feces.

Methods: FMT was performed in 12 patients, 8 with refractory diarrhea-predominant IBS and 4 with functional diarrhea (FDr), who were refractory to medical therapy. The donors were family members within a second degree of kinship and differed for each transplant. Fecal characteristics were evaluated before and 12 weeks after transplantation using the Bristol stool scale (BS). BS scores of 3-5 at 12 weeks after transplantation were considered to indicate responders, while BS scores of 6 and 7 indicated nonresponders. Metagenomic and metabolomic analyses of all 12 donor fecal samples were performed to compare the responder and nonresponder groups.

Results: Before transplantation, all patients had BS scores of 6-7, but 12 weeks after transplantation, 6 were considered responders and 6 were nonresponders. Metagenomic analysis showed that effective donor feces contained significantly higher levels of Prevotella than did the ineffective donor feces. Metabolomic analysis showed that effective donor feces contained significantly higher levels of propionate and butyrate and significantly lower lactate levels than did ineffective donor feces.

Conclusion: Propionate-, butyrate-, or Prevotella-rich donor feces may contribute to successful FMT in patients with diarrhea-dominant functional gastrointestinal disorders.