Self-reported bowel symptoms are associated with differences in overall gut microbiota composition and enrichment of Blautia in a population-based cohort

Background and Aim: Altered gut microbiota have been suggested as part of an etiology of irritable bowel syndrome (IBS), but studies have shown contrasting results. Our aim was to examine gut microbiota composition in a large population-based cohort, with respect to presence and severity of bowel symptoms. Methods: The study cohort consisted of 1988 participants of the Malmö Offspring Study (mean age 40 years, 53% women). From a questionnaire, 19% reported having bowel symptoms the last 2 weeks and 15% reported having IBS. Bowel symptoms were assessed by a validated set of questions with visual analog scales. Gut microbiota was assessed by 16S rRNA gene sequencing (300 bp*2 in V1–V3 region) from fecal samples. The association between abundance of bacteria at genus level and bowel symptoms was calculated by logistic regression or general linear model, adjusted for false discovery rate (q < 0.05). Results: Self-reported bowel symptoms (P = 0.003) and IBS (P = 0.031) were associated with difference in overall gut microbiota composition (beta-diversity). Additionally, bowel symptoms and IBS were associated with increased abundance of Blautia, and bowel symptoms also with a genus in the SHA98 order and Butyricimonas. Pain was associated with increased abundance of Fusobacterium. Diarrhea was associated positively with [Prevotella] and Blautia and negatively with a genus in the SHA98 order and a genus in the Christensenellaceae family. Conclusion: Self-reported bowel symptoms are associated with differences in overall gut microbiota composition and abundancy of a few specific bacteria at genus level in a population-based cohort. Diarrhea is the individual symptom with most associations