AUTHOR=Abdelbary Mohamed M. H. , Hatting Maximilian , Bott Alexandra , Dahlhausen Andrea , Keller Doris , Trautwein Christian , Conrads Georg 

TITLE=The oral-gut axis: Salivary and fecal microbiome dysbiosis in patients with inflammatory bowel disease

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=Volume 12 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2022.1010853

DOI=10.3389/fcimb.2022.1010853

ISSN=2235-2988

ABSTRACT=Inflammatory bowel disease (IBD) is a group of chronic inflammatory disorders that fall into two main categories: Crohn’s disease (CD) and ulcerative colitis (UC). The gastrointestinal tract extends from the mouth to the anus and harbors diverse bacterial communities. Several sequencing-based studies have identified an intestinal enrichment of oral-associated bacteria and demonstrated their ability to induce intestinal inflammation in mice, suggesting that intestinal pathobionts originate from the oral cavity, particularly members of the genus Streptococcus. This study aimed to investigate the composition of the salivary and fecal microbiome of IBD patients (n = 14) compared to healthy controls (n = 12) and to determine the abundances of common bacterial taxa in both niches. Metagenomic DNA was extracted from saliva and fecal samples, and the V3–V4 region of the 16S rRNA gene was targeted for sequencing using Illumina MiSeq. Our results revealed that the overall microbial composition of saliva was significantly altered in the IBD patients compared to the control subjects (p = 0.038). At the genus level, Veillonella and Prevotella were highly abundant in IBD (median: 25.4% and 22.2%, respectively) compared to the control group (17.9% and 13.4%, respectively). In contrast, Neisseria, Streptococcus, Haemophilus, and Fusobacterium were associated with a healthy gut state. Regarding the fecal microbiome, IBD patients had a significantly higher abundance of Clostridium sensu stricto 1 and Escherichia-Shigella compared with the control group, which was also associated with significant upregulation of metabolic pathways, including bacterial invasion of epithelial cells. Streptococcus was the only genus detected in both the salivary and fecal microbiome and represented the oral-gut axis in our study. Using culture-based methods, we isolated 57 and 91 Streptococcus strains from saliva and 40 and 31 strains from fecal samples of the controls and IBD patients, respectively. The phylogenetic tree of streptococci based on sodA sequences revealed several patient-specific clusters comprising salivary and fecal streptococcal isolates from the same patient and belonging to the same species, suggesting that the oral cavity is an endogenous reservoir for intestinal strains.