Predictors of Treatment Response to Fecal Microbiota Transplantation in Irritable Bowel Syndrome: A Pilot Study

We aim to investigate the effectiveness, safety, and predictors of treatment response to fecal microbiota transplantation (FMT) in Korean irritable bowel syndrome (IBS) patients.

Patients with moderate to severe diarrhea-predominant IBS (IBS-D) or mixed-type IBS (IBS-M) received FMT from one healthy donor via esophagogastroduodenoscopy. IBS-symptom severity score (IBS-SSS), Bristol stool form scale (BSFS), IBS Quality of Life (IBS-QoL) questionnaires, Hospital Anxiety and Depression Scale (HADS), and gut microbiome profiles were assessed at baseline, 4 weeks and 12 weeks post-FMT.

Among the 46 enrolled IBS patients, 37 patients (IBS-D:IBS-M = 28:9) completed a 12-week follow-up. Significant improvements were observed in IBS-SSS, IBS-QoL, and BSFS after 12 weeks. FMT led to increased microbial diversity and a sustained increase in beneficial bacterial genera, including Holdemanella, Ruminococcus, and Faecalibacterium. In terms of β-diversity, the distance between the patient's gut microbiome and that of the donor decreased after FMT; greater reduction in distance to donor microbiota was associated with greater symptom improvement (Unweighted UniFrac distance, P < 0.05). Responders (IBS-SSS reduction > 50 points) exhibited lower baseline relative abundances of Roseburia and Subdoligranulum, and more profound microbiome shifts toward the donor profile after FMT.

FMT appears to be a potentially effective treatment for moderate to severe IBS, with significant symptom relief and gut microbiota changes. Lower baseline abundances of Roseburia and Subdoligranulum and greater shifts of gut microbiome profile toward donor microbiota after FMT may predict favorable FMT response. Long-term follow-up is on the way to assessing the durability of these effects.