Gut Microbiota Alterations and Dysbiosis Patterns in Pediatric Inflammatory Bowel Disease: Clinical Correlations and Therapeutic Impact.

Background: Gut microbiota alterations are increasingly recognized as key contributors to the development and clinical course of inflammatory bowel disease (IBD), particularly in pediatric patients, in whom microbial maturation and immune regulation are still evolving. Objective: This study aimed to assess intestinal microbiota composition and dysbiosis severity in pediatric IBD, with comparative analyses according to disease phenotype (Crohn's disease versus ulcerative colitis) and therapeutic strategy (biologic versus non-biologic treatment). Methods: A prospective cohort of 60 pediatric patients diagnosed with IBD based on Porto criteria was evaluated. Fecal samples were obtained at baseline and after three months of combined standard IBD treatment and adjunct microbiota-targeted therapy, and were analyzed using an AI-assisted microbiota profiling platform. A semi-quantitative dysbiosis score was calculated based on the relative abundance of proinflammatory taxa and depletion of short-chain fatty acid (SCFA)-producing bacteria. Microbial parameters were correlated with clinical and therapeutic variables, including the Organism of Interest metric and the Gut Microbiota Index (GMI). Results: Dysbiosis severity was significantly higher in patients with Crohn's disease compared with ulcerative colitis (9.65 ± 1.44 vs. 8.42 ± 1.88, p = 0.037). Patients receiving biologic therapy showed a trend toward lower dysbiosis scores and improved microbial indices, although statistical significance was not reached. Severe dysbiosis was identified in 46.7% of the cohort. Strong positive correlations were observed between the dysbiosis score, Organism of Interest metric and GMI (r = 0.68-0.72, p < 0.01). Conclusions: Pediatric IBD is associated with a reproducible dysbiotic profile, more pronounced in Crohn's disease and partially modulated by biologic therapy. The observed correlations between microbiota-derived indices support their potential utility as complementary markers of intestinal microbial imbalance and disease activity.