Oral microbiome diversity and composition in inflammatory bowel disease patients with periodontitis

Background Inflammatory bowel disease (IBD) and periodontitis are chronic inflammatory disorders sharing immune dysregulation and microbiota imbalance. The oral microbiota may influence IBD through the ‘oral-gut axis.’Methods Using 2009–2010 NHANES data, we performed 1:1 propensity score matching (age and sex), yielding 50 IBD patients and 50 controls. Periodontitis was defined by CDC/AAP criteria; IBD by self-reported physician diagnosis. Weighted multivariable logistic regression assessed the periodontitis–IBD association. Oral microbiome data from 16S rRNA sequencing were analyzed for α/β-diversity, differential taxa (ANCOM-BC, random forest, LEfSe), co-occurrence networks, and correlations with systemic inflammatory markers.Results Periodontitis was significantly associated with increased IBD risk (OR = 4.82, 95% CI: 1.15–20.15, P = 0.031). The IBD group showed reduced Shannon diversity (P = 0.045) without significant β-diversity differences. Differential genera included enrichment of Curvibacter and Cloacibacterium in IBD, and Porphyromonas and Fusobacterium in controls. Co-occurrence networks revealed sparser interactions and altered hub genera in IBD. Correlations with inflammatory markers were generally weak.Conclusion Periodontitis is independently associated with prevalent IBD. IBD patients exhibit reduced oral microbial diversity and compositional shifts. These findings support the ‘oral-gut axis’ hypothesis and suggest oral microbiota as potential non-invasive indicators for further validation.