A novel, strong association has been identified between the Brachyspira genus and irritable bowel syndrome (IBS), according to a study published in Gut.

An increased incidence of IBS after an episode of gastroenteritis suggests microbial perturbation as an underlying factor; however, studies of fecal microbiota in IBS have not demonstrated reproducible alterations. Thus, a team of researchers investigated potential associations between mucus-resident microbiota and IBS symptoms by prospectively collecting mucus samples from sigmoid colon biopsies obtained from patients with IBS and volunteers without IBS, and analyzing their microbial protein composition through mass spectrometry.

The investigators found potentially pathogenic Brachyspira species in the colonic mucosa of 31% of patients with IBS but not in any individual without IBS. The prevalence of Brachyspira colonization in IBS with diarrhea (IBS-D) was 40% in both groups (P=.02 and P=.006 vs controls). One-fifth of patients with IBS were found to have Brachyspira attachment to the colonocyte apical membrane, which was associated with accelerated oro-anal transit, mild mucosal inflammation, mast cell activation, and alterations of molecular pathways linked to bacterial uptake and ion-fluid homeostasis. Treatment with metronidazole paradoxically promoted Brachyspira relocation into goblet cell secretory granules, possibly representing a novel bacterial strategy to evade antibiotics.


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The study had some limitations, including that its observational nature did not allow the researchers to establish a causal relationship between Brachyspira and IBS symptoms. In addition, suboptimal biopsy specimens and technical failures resulted in a small proportion of missing data for certain methods, although with no systematic bias between participant categories.

The authors concluded, “Mucosal Brachyspira colonisation was significantly more common in IBS and associated with distinctive clinical, histological and molecular characteristics.” They added, “Our observations suggest a role for Brachyspira in the pathogenesis of IBS, particularly IBS-D.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

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Reference

Jabbar KS, Dolan B, Eklund L, et al. Association between Brachyspira and irritable bowel syndrome with diarrhoea. Gut. Published online November 11, 2020. doi:10.1136/gutjnl-2020-321466