Background and objectiveAlthough infliximab (IFX) is endorsed for induction therapy in severe ulcerative colitis (SUC), its therapeutic response remains heterogeneous. We conducted a comprehensive analysis of fecal and mucosal microbiota, coupled with targeted metabolomics, to delineate microbial and metabolic signatures predictive of IFX induction efficacy and to explore mechanistic pathways underlying differential treatment responses.MethodsThis study was a prospective cohort study (clinical s