Transitional and temporal changes in the mucosal and submucosal intestinal microbiota in advanced Crohn's disease of the terminal ileum.

PURPOSE: Crohn's disease is a chronic debilitating intestinal syndrome of unknown aetiology that is thought to result in part from an imbalance (dysbiosis) of the intestinal microbial populations, known as the microbiota. In this study we sought to compare the microbiota at the mucosal and submucosal levels at the resection margin in Crohn's disease to those in other intestinal dysbiotic disease controls to determine the level of bacterial translocation.

METHODOLOGY: 16S microbiota sequencing was performed on DNA extracted from mucosal and submucosal samples from resected intestinal tissues from Crohn's disease and controls.

RESULTS

Grossly normal appearing tissue at the resection margin showed early signs, suggesting bacterial translocation, with two bacterial families having penetrated the mucosal surfaces. In contrast, 4 and 13 bacterial families were present within submucosal tissues at the disease centre and disease margin, respectively. Although there was no significant difference in biodiversity, there was increased bacterial richness in the Crohn's disease group as compared to non-IBD controls.

CONCLUSION

The presence and/or absence of certain bacteria suggested disease-specific ecological or micro-environmental pressures driving or excluding certain organisms in Crohn's disease. The data suggest that several of the dysbiotic conditions previously reported for Crohn's disease are not unique but common to general dysbiosis. The examination of multiple intestinal sites in advanced disease may provide a spectrum of disease from early onset at the resection margin to active disease at the disease margin and late-stage fibrostenotic disease at the centre of the lesion, and a unique etiopathogenic view of Crohn's disease.