Characterization of the salivary microbiome of adults with inflammatory bowel disease

Background: Perturbations of the gut microbiota in patients with inflammatory bowel disease (IBD) have been extensively characterised, but changes to the oral microbiome remain understudied. This study aimed to evaluate the oral microbiome of adults with IBD and of matched controls. Methods: Saliva samples and data were obtained from a Canadian population cohort (n = 320). The salivary microbiome was characterised using 16S rRNA gene sequencing and examined for differences between control participants and those with IBD, as well as disease subcategories (Crohn’s Disease and Ulcerative Colitis). Results: Alpha diversity was significantly lower in participants with IBD than controls in unadjusted models and many remained significant after adjusting for covariates. Significant differences in some beta diversity metrics between participants with IBD and controls were found, although these did not remain significant when adjusted for covariates. Ten genera were significantly differentially abundant between cases and controls. Veillonella and Streptococcus were both increased in abundance in IBD cases vs controls (25% vs 22% and 14% vs 12%, respectively). Conclusion: These results showcase changes in oral microbial diversity and composition in those living with IBD and highlight the potential of using the salivary microbiome as a biomarker for screening or monitoring IBD.