M El-Salhy et al. Gastroenterol 2022; 163: 982-994. Open Access! Efficacy of Fecal Microbiota Transplantation for Patients With Irritable Bowel Syndrome at 3 Years After Transplantation
Background: “Fecal microbiota transplantation (FMT) might be a promising treatment for IBS, and this has been investigated in 7 randomized controlled trials (RCTs). 2 In 4 of these, FMT reduced symptoms and improved the quality of life of patients with IBS, whereas no effects were indicated in the other 3. 2 The difference in these results was likely because of differences in the protocols used, the selected donors, the cohort of treated patients, the fecal transplant dose, and the route by which the transplant was administrated.2“
Methods: In this placebo-controlled trial with 125 patients, fecal microbiota transplantation (FMT) was administered into duodenum (30 g or 60 g). The donor was a healthy male aged 36 years with a normal body mass index who was born via vaginal delivery, breastfed, a nonsmoker, was not taking any medication, was only treated a few times with antibiotics, exercised regularly, and consumed a sport-specific diet that was richer in protein, fiber, minerals, and vitamins than the average diet.
Key findings:
- Response rates were 26.3%, 69.1%, and 77.8% in the placebo, 30-g, and 60-g groups, respectively, at 2 years after FMT, and 27.0%, 64.9%, and 71.8%, respectively, at 3 years after FMT.
- Fluorescent signals of 10 bacteria had significant correlations with IBS symptoms and fatigue after FMT in the 30-g and 60-g groups.
- No long-term adverse events were recorded. The authors note in the discussion rare serious safety issues with FMT but indicate in this population without systemic diseases or immune deficiency, that adverse effects were mild and self-limited gastrointestinal symptoms
The associated editorial (815–817, Treatment of Irritable Bowel Syndrome Using Fecal Microbiota Transplantation: A Step Forward?) noted that 25% of patients in the donor FMT continue to experience severe symptoms based on IBS-SSS>300; in addition, 50% (in 30 g) and 40% (in 60 g) had moderately severe IBS scores >175.
The editorial suggests that overall response is modest bust similar to FDA-approved medications for IBS. The number needed to treat (NNT) would be 4-5 patients to reduce the proportion with severe IBS-SSS based on per-protocol analysis (most IBS medications range from 6 to 10).

My take: This study strengthens the notion that alterations in our microbiome can the outcomes of patients suffering from IBS. Now, we have to identify which patients will benefit from this approach and how to optimally modify the microbiome. In addition, this study suggests that finding an optimal FMT donor will impact results given variability in prior trials.
Related blog posts:
- FMT Research & The Shawshank Redemption
- Fecal Microbial Transplantation -Evidence for Use Beyond Recurrent Clostridium Difficile | gutsandgrowth
- Long-term Safety of Fecal Microbiota Transplantations | gutsandgrowth

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