Bifidobacterium stercoris KC84 attenuates IBS-D-like symptoms via modulation of serotonin-related pathways and dendritic cell-mediated IFN-β induction

Serotonin dysregulation, primarily driven by enterochromaffin cells in the intestinal epithelium, is central to IBS-D pathogenesis. We hypothesized that targeted modulation of enterochromaffin cell activity through microbiome-based interventions could provide a novel treatment approach.

Here, we screened 128 Bifidobacterium isolates and identified B. stercoris KC84 as a promising candidate. KC84 alleviated IBS-D symptoms in both chemically and stress-induced models, accompanied by reduced serotonin levels. Transcriptomic analysis revealed activation of type I interferon (IFN)-associated pathways, corroborated by ex vivo evidence of KC84-induced IFN-β secretion, predominantly from type 1 conventional dendritic cells.