Fecal Microbiota Signatures Are Not Consistently Related to Symptom Severity in Irritable Bowel Syndrome

Abstract

Background Irritable bowel syndrome (IBS) is the most prevalent functional bowel disorder, but its pathophysiology is still unknown. Although a microbial signature associated with IBS severity has been suggested, its association with IBS severity still remains largely unknown. Aims This study aims to assess longitudinal dynamics of fecal microbiota and short-chain fatty acids (SCFAs) in different IBS severity groups and study the association with stool pattern, diet, depression, anxiety, and quality of life (QoL). Methods A longitudinal study was performed, including n = 91 IBS patients and n = 28 matched controls. All participants collected fecal samples for microbiota composition and SCFA analysis and completed validated questionnaires regarding IBS severity, stool pattern, depression, anxiety, and IBS-QoL at two timepoints with four weeks in-between. Diet was assessed at the first timepoint. Results Over time, 36% of IBS patients changed in severity group, and 53% changed in predominant stool pattern. The largest proportion of microbiota variation was explained by the individual (R 2 = 70.07%). Microbiota alpha diversity and composition, and SCFAs did not differ between IBS severity groups, nor between IBS and controls. Relative abundances of Bifidobacterium, Terrisporobacter, and Turicibacter consistently differed between IBS and controls, but not between IBS severity groups. Large dynamics over time were observed in the association of microbiota composition with questionnaire data where IBS symptom severity was associated at T1 but not at T2. Conclusions Fecal microbiota and SCFA signatures were not consistently associated with IBS severity over time, indicating the importance of repeated sampling in IBS research.

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“…The details of the study design, subject recruitment, questionnaire data collection, and fecal microbiota composition profiling were described previously ( 35 ). Briefly, this was an observational study that included two time points ( T 1 and T 2 ) with 4 weeks in between.…”

“…The fecal microbiota composition was determined by sequencing the V4 region of the 16S rRNA gene, and NG-Tax 2.0 was used to process the raw sequence data for amplicon sequencing variant (ASV) picking with default settings and for taxonomic assignments as described previously ( 35 ). Alpha diversity (within-sample diversity) and beta diversity (between-sample diversity) were calculated at the ASV level using Phyloseq ( 45 ).…”

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