Abstract
BackgroundThe gut microbiota is thought to play a key role in the development of the inflammatory bowel diseases Crohn's disease (CD) and ulcerative colitis (UC). Shifts in the composition of resident bacteria have been postulated to drive the chronic inflammation seen in both diseases (the "dysbiosis" hypothesis). We therefore specifically sought to compare the mucosa-associated microbiota from both inflamed and non-inflamed sites of the colon in CD and UC patients to that from non-IBD controls and to detect disease-specific profiles.ResultsPaired mucosal biopsies of inflamed and non-inflamed intestinal tissue from 6 CD (n = 12) and 6 UC (n = 12) patients were compared to biopsies from 5 healthy controls (n = 5) by in-depth sequencing of over 10,000 near full-length bacterial 16S rRNA genes. The results indicate that mucosal microbial diversity is reduced in IBD, particularly in CD, and that the species composition is disturbed. Firmicutes were reduced in IBD samples and there were concurrent increases in Bacteroidetes, and in CD only, Enterobacteriaceae. There were also significant differences in microbial community structure between inflamed and non-inflamed mucosal sites. However, these differences varied greatly between individuals, meaning there was no obvious bacterial signature that was positively associated with the inflamed gut.ConclusionsThese results may support the hypothesis that the overall dysbiosis observed in inflammatory bowel disease patients relative to non-IBD controls might to some extent be a result of the disturbed gut environment rather than the direct cause of disease. Nonetheless, the observed shifts in microbiota composition may be important factors in disease maintenance and severity.
Highlights
The gut microbiota is thought to play a key role in the development of the inflammatory bowel diseases Crohn’s disease (CD) and ulcerative colitis (UC)
Twenty-nine mucosal biopsies were collected from a total of seventeen patients, including paired biopsies of inflamed and non-inflamed tissue from six patients with active CD (n = 12), paired biopsies from six patients with active UC (n = 12) and five biopsies from non-Inflammatory bowel disease (IBD) controls (n = 5)
The results suggest a tendency towards a reduction in Firmicutes and an increase in Bacteroidetes species in IBD patients compared to controls and indicate that there is an increase in Enterobacteriaceae in CD
Summary
The gut microbiota is thought to play a key role in the development of the inflammatory bowel diseases Crohn’s disease (CD) and ulcerative colitis (UC). Inflammatory bowel disease (IBD) encompasses both Crohn’s disease (CD) and ulcerative colitis (UC), chronic inflammatory disorders of the gastrointestinal tract with developed world predominance and an incidence that. The cause of both conditions is still speculative. The current generally accepted disease hypothesis is that the chronic inflammation of IBD results from a genetically dysregulated host immune response directed at the gut microbiota [6,7,8]. A disruption in this homeostasis threatens the state of immune tolerance and may result in gut inflammation
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