Although dysbiosis has often been implicated in the pathogenesis of PI-IBS, the present FMT results suggest that microbiota changes alone are insufficient to drive PI-IBS-like symptoms together with Bdkrb upregulation, as antibiotic-treated WT mice did not exhibit visceral hypersensitivity after FMT with feces from TLR9 KO mice with PI-IBS like symptoms. Here, TLR9 is linked to irritable bowel syndrome.