Specific contributions of segmental transit times to gut microbiota composition

We read with great interest the study by Asnicar and colleagues, describing the exploration of gut microbiota composition in relation to gut transit time using the ‘blue dye’ method.1 In agreement with previous research, the authors provided convincing evidence that longer gut transit times are linked to increasing relative abundances of microbial species (ie, Akkermansia muciniphila, Bacteroides spp. and Alistipes spp. ).1–3 However, despite practical advantages, the ‘blue dye’ method does not allow to distinguish between segmental transit times. In a recent study, we investigated segmental transit time and passage-related variation in pressure and pH in 22 individuals (11 subjects with normal weight and 11 subjects with obesity) using a wireless motility capsule (SmartPill©).4 During capsule passage, participants were asked to collect a faecal sample. Samples were subjected to 16S rRNA gene amplicon sequencing according to Valles-Colomer et al .5 Associations between clinical and SmartPill© variables and faecal microbiota community variation were assessed using single and stepwise multivariate distance-based redundancy analyses (dbRDA). Next, we explored associations between the microbiome covariates identified and participants’ enterotypes using Kruskal-Wallis test with post-hoc pairwise Dunn’s test.6 Finally, correlations between relative abundances of genera and significant variables were assessed …