Unveiling intestinal carriage in healthy volunteers: the role of micro- and mycobiota, diet, host genetics and immune response.

is a commensal yeast present in the gut of most healthy individuals but with highly variable concentrations. However, little is known about the host factors that influence colonization densities. We investigated how microbiota, host lifestyle factors, and genetics could shape intestinal carriage in 695 healthy individuals from the Milieu Intérieur cohort. intestinal carriage was detected in 82.9% of the subjects using quantitative PCR. Using linear mixed models and multiway-ANOVA, we explored intestinal levels with regard to gut microbiota composition and lifestyle factors including diet. By analyzing shotgun metagenomics data and qPCR data, we showed that was the only gut microbiota species whose relative abundance was negatively correlated with concentration. Diet is also linked to growth, with eating between meals and a low-sodium diet being associated with higher levels. Furthermore, by Genome-Wide Association Study, we identified 26 single nucleotide polymorphisms suggestively associated with colonization. In addition, we found that the intestinal levels of might influence the host immune response, specifically in response to fungal challenge. We analyzed the transcriptional levels of 546 immune genes and the concentration of 13 cytokines after whole blood stimulation with cells and showed positive associations between the extent of intestinal levels and expression, as well as secreted IL-2 and CXCL5 concentrations. Taken together, these findings open the way for potential new interventional strategies to curb intestinal overgrowth.