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.

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The reduction in mucosa-associated bifidobacteria and increase in E. coli and clostridia in patients with IBD supports the hypothesis that an imbalance between potentially beneficial and pathogenic bacteria may contribute to its pathogenesis.

OFG mainly presents in young adults with lip and buccal involvement. Abnormalities in inflammatory markers, hematology and oral features of ulceration, and buccal-sulcal involvement are factors more commonly associated with CD. Initial presentation of OFG does not necessarily predict development of CD, although this is more likely in childhood.

Irritable bowel syndrome (IBS) is a chronic disorder characterized by abdominal pain, change in bowel habit, and bloating. It has traditionally been viewed as a disorder of visceral hypersensitivity heavily influenced by stress, and therefore therapeutic strategies to date have largely reflected this. However, more recently, there is good evidence for a role of the gastrointestinal (GI) microbiota in its pathogenesis. Changes in fecal microbiota, the use of probiotics, the phenomenon of postinfectious IBS, and the recognition of an upregulated host immune system response suggest that an interaction between the host and GI microbiota may be important in the pathogenesis of IBS. This article explores the role of the GI microbiota in IBS and how their modification might lead to therapeutic benefit.

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Summary In a double‐blind placebo‐controlled cross‐over trial, low dose sublingual therapy with house dust mite was effective in relieving symptoms in 72% of the group of patients with perennial rhinitis due to house dust mite (P < 0·03). Following active treatment, there was a significant increase in morning peak nasal inspiratory flow rate (P < 0·01) in those who improved (thirteen out of eighteen) and resistance to nasal provocation with house dust mite also increased, in some cases up to 1000‐fold (P < 0·05). Oral therapy is safe and avoids the side effects of desensitizing injections which can be serious. The potential for oral desensitization is great and further studies on this form of treatment are needed.

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