The role of microbiota in inflammatory bowel disease

Crohn's disease and ulcerative colitis are inflammatory diseases of the gastrointestinal tract that together comprise a spectrum of diseases entitled inflammatory bowel disease (IBD). The human intestine is colonized with commensal microbiota in concentrations that exceed the number of cells in the human body. Under normal physiologic conditions there is an interplay between these bacteria and the human host in a process that maintains the integrity of the immune system in health and disease. Gut microbiota play an important role in IBD. Commensal and pathologic bacteria comprise part of the etiology of IBD, and the gut microbiota in patients with IBD is different from that in healthy controls. Their influence is probably brought about in initiation of disease as well as in flare-ups, and it is logical to assume that manipulation of the gut microbiota could be a preventive measure in IBD evolution and may play a therapeutic role in disease exacerbation. This review will briefly discuss issues related to studying gut microbiota, the interplay of these microbiota with the immunologic system in IBD, and focus on the role of microbiota in the etiology, flare-ups and treatment of IBD.