Patient-donor similarity and donor-derived species contribute to the outcome of faecal microbiota transplantation for ulcerative colitis.

Background and aims: Clinical applications of faecal microbiota transplantation (FMT) for treating ulcerative colitis (UC) have shown promising results. However, whether the beneficial effects of FMT are due to the transfer and colonisation of donor-derived species in patients remains unclear. Here, we investigated the factors affecting the efficacy of administration of triple antibiotics (A-FMT) and the criteria for appropriate donor and patient-donor matching.

Methods: Ninety-seven patients with active UC who were enrolled between March 2014 and October 2019 underwent FMT. The clinical features were assessed based on a reduction in Lichtiger's clinical activity index 4 weeks after A-FMT, with long-term responders (LTR) defined as those with no increase or intensification within 12 months after A-FMT. Microbiome analysis was performed on 147 faecal samples (pre-A-FMT, post-A-FMT, and donor) from 49 patient-donor combinations that were assigned using the one patient-to-one donor strategy.

Results: Of the 97 patients, 61 achieved a clinical response, and of those, 35 were classified as having clinical remission. The efficacy of A-FMT was affected by UC severity and previous administration of steroids (p = 0.027), immunosuppressants (p = 0.049), and biologics (p = 0.029). Effective donors were rich in taxa such as Bacteroidota, which are lost in UC, and the abundances of "patient-origin" and "new-amplicon sequence variant" taxa were significantly lower in Responders compared to Nonresponders (Remission; p = 0.03, LTR; p = 0.05). "Donor-derived" amplicon sequence variant sequences, Oscillospiraceae UCG-002 and Alistipes, were significantly enriched in Responders (p < 0.05). Our results showed that the taxonomic composition of patients and the similarity of Bacteroides and butyric acid-producing bacteria in the patient-donor microbiota significantly influenced A-FMT efficacy (p < 0.05).

Conclusions: This study provides important insights for developing patient-tailored FMT-based therapies for UC.