Donor composition and fiber promote strain engraftment in a randomized controlled trial of fecal microbiota transplant for ulcerative colitis.

BACKGROUND: Fecal microbiota transplantation (FMT) is an emerging treatment for ulcerative colitis (UC), but the impact of prebiotic fiber on FMT efficacy for UC is unclear. We performed a randomized, double-blind, placebo-controlled clinical trial to examine the efficacy of FMT with and without dietary fiber supplementation in patients with UC. METHODS: 27 patients with mild to moderate UC were randomized to receive a single FMT or placebo with or without psyllium fiber supplementation for 8 weeks. The primary outcome was clinical response at week 8, and secondary outcomes included endoscopic improvement and clinical remission. Metagenomic sequencing of fecal DNA was analyzed to determine taxonomic profiles and donor strain engraftment. FINDINGS: The trial was terminated early due to manufacturer discontinuation of FMT product. FMT induced clinical response, remission, and endoscopic improvement in UC patients compared to placebo (p < 0.05), but fiber did not improve clinical outcomes of FMT. Recipient microbiome composition post-FMT shifted toward donor composition in responders and non-responders, but the durability of this change was stronger in responders. Clinical response and durable change in microbiome composition following FMT was donor dependent. Strain tracking analysis also demonstrated a donor-dependent variability in the rate of successful engraftment and identified a consortium of engrafted bacteria associated with treatment response or fiber supplementation. CONCLUSIONS: Single-dose FMT demonstrated clinical efficacy for mild to moderate UC compared to placebo but revealed no benefit of fiber supplementation. These results highlight proof of concept that donor selection and prebiotic fiber can shape strain-level engraftment. This study was registered at ClinicalTrials.gov: NCT03998488. FUNDING: National Institutes of Health/National Institute of Diabetes and Digestive and Kidney Diseases (R01 DK128257, to R.S.L.).