The role of bacteria in the inflammatory bowel disease development: a narrative review

Inflammatory bowel disease (IBD) is a general term used for the ulcerative colitis (UC) and Crohn's disease (CD); in addition, IBD principally refers to a chronic disease of the gastrointestinal tract in which mediated by immune system. Consequently, IBD could progress in individuals who are genetically prone. Infections role in the development of inflammatory disease of the gastrointestinal tract has been studied by quite many clinical studies; furthermore, the possible role of some pathogens in the development and exacerbation of the inflammatory disease of the gastrointestinal tract have been described. Evidently, the most indispensable pathogens that could be associated with the IBD disease, Mycobacterium avium subspecies paratuberculosis, Clostridium difficile, Escherichia coli, Listeria monocytogenes, Campylobacter concisus; as well as viruses, such as, cytomegalovirus, Epstein-Barr Virus, and measles virus are notable. A number of pathogenic parasites may also be involved in the development and progression of the disease. As a matter of fact, overexposure of immune system in the presence of excessive bacterial substances could also lead to the loss of immunological tolerance to the bacteria, which are commonly considered as the normal flora in the intestine; furthermore, it may subsequently elicit bowel inflammation and IBD development. In the current study, we discussed the most common bacterial pathogens that may be involved in the development of IBD; as well as, a comprehensive narrative review related to the evidences which support or ignore the possible role of bacteria in progression of IBD, indeed.