The Role of the Microbiome in the Etiology of Inflammatory Bowel Diseases.

Inflammatory bowel diseases (IBDs) result from dysregulated immune responses to environmental and microbial triggers in genetically susceptible hosts. Many clinical observations and animal studies support the role of the microbiome in the pathogenesis of IBD. Restoration of the fecal stream leads to postoperative Crohn's recurrence, while diversion can treat active inflammation. Antibiotics can be effective in prevention of postoperative Crohn's recurrence and in pouch inflammation. Several gene mutations associated with Crohn's risk lead to functional changes in microbial sensing and handling. However, the evidence linking the microbiome to the IBD is largely correlative, given the difficulty in studying the microbiome before disease occurs. Attempts to modify the microbial triggers of inflammation have had modest success to date. Exclusive enteral nutrition can treat Crohn's inflammation though no whole food diet to date has been shown to treat inflammation. Manipulation of the microbiome through fecal microbiota transplant and probiotics have had limited success. Further focus on early changes in the microbiome and functional consequences of microbial changes through the study of metabolomics are needed to help advance the field.