Reduced abundance of butyric acid-producing bacteria in the ileal mucosa-associated microbiota of ulcerative colitis patients

Compositional changes in the microbiota are associated with various inflammatory diseases, including ulcerative colitis (UC). Aim: This study aimed to investigate the mucosa-associated microbiota (MAM) in patients with UC and its difference related with disease activity and classification. Brush samples were collected from the terminal ileum and sigmoid colon during endoscopic procedures. The microbiota of samples was profiled using the Illumina MiSeq platform. The V3–V4 regions of the gene encoding 16S rRNA (460 bp) were amplified using PCR. Fifty UC patients and twenty healthy controls were enrolled. UC patients displayed significantly reduced α-diversity in both the ileum and sigmoid colon compared to controls. A difference in β-diversity in the unweighted analysis was observed between the two groups. The abundance of Lactobacillus and Veillonella was significantly higher and that of Butyricicoccus, Ruminococcus and Lachnospiraceae was significantly lower in the ileum of UC patients than in controls. The abundance of Odoribacter in the ileum was significantly lower in left-sided colitis and pancolitis patients than in proctitis patients and lower in patients with highly severe disease activity than with mild disease activity. The reduction in abundance of butyric acid-producing bacteria, especially Odoribacter, in ileal MAM may play an important role in the pathophysiology of UC.