Similar Gut Bacterial Composition Between Patients With Ulcerative Colitis and Healthy Controls in a High Incidence Population: A Cross-sectional Study of the Faroe Islands IBD Cohort

Background The Faroe Islands has the world's highest incidence of inflammatory bowel disease (IBD). Epidemiological studies have characterized this unique cohort and a decreased risk of developing IBD with emigration. Therefore, this well-characterized Faroese IBD cohort gives the opportunity to better understand this complex disease. This study represents the first investigation of the gut microbiota for the cohort. Methods This cross-sectional study consisted of 41 patients with established ulcerative colitis and 144 age- and sex-matched healthy controls recruited through the Faroe Genome project. Participants donated a 1-time fecal sample and completed questionnaires on food frequency, background health, and lifestyle. 16S rRNA amplicon sequencing of the V3-V4 region was performed followed by bioinformatic analysis of taxonomy and diversity metrics. Results The overall bacterial composition in both groups was dominated by Firmicutes and Bacteroidetes. No significant differences were found based on metrics of alpha or beta diversity. However, discriminatory analysis identified differential abundance of several indicator taxa in healthy controls and ulcerative colitis participants, whereas Akkermansia was completely absent from 27% of all study participants. Food frequency questionnaires revealed similar dietary patterns between the 2 groups. Conclusion The similarity in bacterial community composition and absence of the beneficial Akkermansia genus in both groups raise further questions concerning the underlying susceptibility toward inflammatory disorders within this high-risk population. Results vary widely by study design and geographic location, which speaks to the need for regionally tuned reference groups and disease-based studies on the Faroe Islands. Lay Summary The Faroe Islands has the world's highest incidence of IBD. This is the first investigation characterizing gut microbiota for this unique cohort. No significant differences were found between ulcerative colitis and healthy controls based on alpha or beta diversity.