Persistent Gut Microbiota Dysbiosis in Pediatric Crohn's Disease: A Next-Generation Sequencing Pilot Study

Background: Crohn's disease (CD) is characterized by gut microbiota alterations including reduced microbial diversity, loss of commensal species, and increased abundance of opportunistic taxa. Methods: This prospective study was conducted between 2022 and 2024 at the Emergency Clinical Hospital for Children, Cluj-Napoca. Children with CD and healthy controls were evaluated. The gut microbiota was analyzed using shotgun metagenomics. Bioinformatic processing assessed alpha and beta diversity, core microbiome composition, and differential taxa. Results: Ten patients with CD and eight healthy children were included; five patients were re-evaluated after a median interval of 14 weeks. The Shannon index was significantly lower in CD patients compared with controls (p = 0.037). Beta diversity analysis suggested partial separation between CD at diagnosis and controls (p = 0.041). An inverse correlation was observed between the Shannon index and the clinical score (p = 0.028). Ruminococcus gnavus was among the taxa contributing to group separation. At follow-up, all patients were in clinical remission, while 80% had achieved biological remission and mucosal healing. They showed persistently reduced alpha diversity and distinct microbial communities compared with controls (p = 0.028 and p = 0.005, respectively). Conclusions: Pediatric CD was correlated with dysbiosis that persisted despite remission. Reduced alpha diversity was associated with greater disease severity at diagnosis.