Abstract
IntroductionStool consistency has been associated with fecal microbial composition. Stool consistency often varies over time, in subjects with and without gastrointestinal disorders, raising the question whether variability in the microbial composition should be considered in microbiota studies. We evaluated within-subject day-to-day variability in stool consistency and the association with the fecal microbiota in irritable bowel syndrome (IBS) and healthy subjects, over seven days.MethodsTwelve IBS patients and 12 healthy subjects collected fecal samples during seven consecutive days. Stool consistency was determined by the patient-reported Bristol Stool Scale (BSS) and fecal dry weight percentage. 16S rRNA V4 gene sequencing was performed and microbial richness (alpha diversity; Chao1 index, observed number of species, effective Shannon index) and microbial community structure (beta diversity; Bray-Curtis distance, generalized UniFrac, and taxa abundance on family level) were determined.ResultsLinear mixed-effects models showed significant associations between stool consistency and microbial richness, but no time effect. This implies that between-subject but not within-subject variation in microbiota over time can partially be explained by variation in stool consistency. Redundancy analysis showed a significant association between stool consistency and microbial community structure, but additional linear mixed-effects models did not demonstrate a time effect on this.ConclusionThis study supports an association between stool consistency and fecal microbiota, but no effect of day-to-day fluctuations in stool consistency within seven days. This consolidates the importance of considering stool consistency in gut microbiota research, though confirms the validity of single fecal sampling to represent an individual’s microbiota at a given time point. NCT00775060.
Highlights
Stool consistency has been associated with fecal microbial composition
71 and 78 samples were available for the irritable bowel syndrome (IBS) and healthy group, respectively
Bristol Stool Scale (BSS) scores showed high day-to-day variability in both groups (ICC for IBS: 0.397; intra-class correlations (ICC) for healthy controls (HC): 0.276). This variability in stool consistency is illustrated in Supplementary Figure 1
Summary
Stool consistency has been associated with fecal microbial composition. Stool consistency often varies over time, in subjects with and without gastrointestinal disorders, raising the question whether variability in the microbial composition should be considered in microbiota studies. Stool consistency measured with the Bristol Stool Scale (BSS) or fecal moisture has been associated with gut microbiota diversity and composition (Tigchelaar et al, 2016; Vandeputte et al, 2016), and has been identified as important covariate of the microbiota composition in population-based studies (Falony et al, 2016; Vandeputte et al, 2017). This indicates the importance of considering stool consistency as a potential confounding factor in both cross-sectional and longitudinal intestinal microbiota analyses. In cross-sectional studies changes in microbial composition have been correlated to IBS symptom scores (Malinen et al, 2010; Rajilic-Stojanovic et al, 2011; Jeffery et al, 2012), which generally vary over time
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