Microbial factors in inflammatory bowel disease
Section snippets
Theoretical role of microbial factors in cause of inflammatory bowel disease
Microbial factors are involved intimately in all the major etiologic theories of IBD that currently are under consideration: (1) IBD develops as an appropriate reaction to a specific persistent pathogenic infection of the intestine, (2) IBD results from subtle alterations in bacterial function and composition (dysbiosis), (3) IBD results from an overwhelming exposure to resident normal luminal bacterial products because of a defective mucosal barrier, and (4) IBD results from an aberrant host
Role of luminal contents in pathogenesis of inflammatory bowel disease
Since 1939, a series of clinical reports and laboratory investigations have suggested that the intestinal fecal stream may play a significant role in the pathogenesis of CD [50]. Although it has been known for some time that the rate of recurrence of CD is lower after end ileostomy than after reanastomosis [45], initial work tended to minimize the importance of fecal stream, suggesting that it may play a role in contributing to secondary tissue damage after inflammation had begun. In an effort
Role of pathogens in induction and relapse of inflammatory bowel disease
Although no confirmed primary pathogen has been identified in IBD patients, abundant evidence documents that common pathogens can precede the onset of IBD, exacerbate symptoms, and reactivate quiescent disease [95]. These potentiating effects may be mediated by breaking the epithelial barrier or initiating a mucosal inflammatory response, leading to chronic idiopathic IBD in the genetically susceptible host. It is not unusual for patients to relate onset of symptoms of IBD to foreign travel or
Role of bacteria in extraintestinal inflammation
Systemic uptake and distribution of bacterial components and inflammatory mediators by mesenteric lymphatics and the portal circulation can lead to extraintestinal manifestations of IBD and experimental colitis [95], [97]. Of UC patients, 27% have portal vein bacteremia [9], and IBD patients have an increased incidence of bacterial endocarditis and hepatic abscesses [54]. Excessive proliferation of anaerobic bacteria in the small intestine can lead to arthritis, uveitis, and liver disease
Antibiotic therapy in Crohn's disease
Despite the putative central role for bacterial flora in IBD pathogenesis and strong experimental support from animal models [75], there are no definitive, multicenter, controlled trials assessing the role of antibiotics in IBD therapy. Nevertheless, antibiotics frequently are used empirically in CD. Possible mechanisms of antibiotics in IBD include decreasing the overall concentrations of luminal bacteria, selectively eliminating certain enteric bacterial subsets, diminishing tissue invasion
Summary
An unsolved puzzle in IBD research is whether germs, genes, or a combination of the two with excessive immune responses to gut-associated bacteria explains the pathogenesis of UC and CD. Whatever the answer, there is little doubt that microbial factors are involved intimately in IBD pathogenesis. Although a long search has failed to confirm a direct pathogenic role for a specific infectious agent, compelling evidence suggests that commensal enteric bacteria and their products provide a local
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