Supplementary Material for: An Open-Labeled Study on Fecal Microbiota Transfer in Irritable Bowel Syndrome Patients Reveals Improvement in Abdominal Pain Associated with the Relative Abundance of <b><i>Akkermansia Muciniphila</i></b>

<b><i>Background/Aims:</i></b> The gut microbiota is altered in irritable bowel syndrome (IBS), and microbiota manipulations by diet or antibiotics can reduce its symptoms. As fecal microbiota transfer (FMT) in IBS is still controversial, we investigated the clinical and side effects of FMT in a cohort of IBS patients with recurrent, treatment refractory symptoms, and studied gut microbiota signatures. <b><i>Methods:</i></b> Using an observational, prospective study design, we applied FMTs from one unrelated, healthy donor to 13 IBS patients. Fecal samples of patients and the donor were analyzed by 16S ribosomal RNA amplicon sequencing. <b><i>Results:</i></b> On a symptom level, primarily abdominal pain symptoms were reduced after FMT, and no adverse effects were observed. Studying the microbiome, we found an increase in alpha diversity and changes in the composition of the gut microbiota after FMT. Beta diversity changes after FMT were prominent in a subset of 7 patients with microbiota profiles coming very close to the donor. These patients also showed most pronounced visceral pain reduction. The relative abundance of <i>Akkermansia muciniphila</i> was inversely correlated with pain reduction in our cohort. <b><i>Conclusion:</i></b> Although exploratory in nature and with a pilot character, this study highlights the potential role of microbiota manipulations in IBS and describes a novel association of intestinal <i>Akkermansia</i> and pain modulation.