Lower fecal microbiota transplantation ameliorates ulcerative colitis by eliminating oral-derived Fusobacterium nucleatum and virulence factor.

Background: Recently, the oral oncobacterium Fusobacterium nucleatum (F. nucleatum), has been linked with ulcerative colitis (UC). Here, we aim to investigate whether Fecal Microbiota Transplantation (FMT) can alleviate UC by restoring gut microbiota and eliminating oral-derived F. nucleatum and virulence factor fadA.

Method: C57BL/6J mice were randomly divided into a healthy control group (HC), Dextran Sulfate Sodium group (DSS), oral inoculation group (OR), upper FMT group (UFMT), and lower FMT group (LFMT). Disease activity index, body weight, survival rate, and histopathological scores were used to measure the severity of colitis. The function of the intestinal mucosal barrier was evaluated by performing immunohistochemical staining of the tight junction protein Occludin. Real-time PCR was used to assess the relative abundance of the nusG gene and the virulence gene fadA. Cytokine levels were detected by ELISA. Full-length sequencing of 16S rRNA was used to analyze the changes and composition of gut microbiota.

Findings: Oral incubation of F. nucleatum further exacerbated the severity of colitis and gut dysbiosis. Peptostreptococcaceae, Enterococcaceae, and Escherichia coli were significantly enriched in OR mice. However, LFMT mice showed an obvious decrease in disease activity and were more effective in restoring gut microbiota and eliminating F. nucleatum than UFMT mice. Bacteroidota, Lachnospiraceae, and Prevotellaceae were mainly enriched bacteria in LFMT mice. In addition, Genera such as Lactobacillus, Allobaculum, and Bacteroidales were found negative correlation with TNF-α, IL-1β, and IL-6. Genera like Romboutsia, Escherichia Shigella, Enterococcus, and Clostridium were found positively correlated with TNF-α, IL-1β, and IL-6.

Conclusions: Oral incubation of F. nucleatum further exacerbates the severity and dysbiosis in DSS-induced colitis mice. Besides, lower tract FMT can ameliorate colitis by restoring the gut microbiota diversity and eliminating F. nucleatum and virulence factor fadA.