Irritable Bowel Syndrome: A Bacterial Culprit

As a lifelong IBS  (irritable bowel syndrome) sufferer, I found this research to be particularly interesting. To date, in comparing fecal microbiome profiles of those with irritable bowel syndrome to those without, there have been no consistent findings.  Fecal samples reflect the bacteria in the lumen of the intestine which is kept separate from the epithelial and immune cells of the intestine by a mucus barrier.  However, some species of bacteria, which feed on mucin (the main component of mucus) have been found to live only in the outer mucus layer. Thus,  researchers at the University of Gothenburg, in Sweden, hypothesized that it may be possible that such bacteria have a major influence on the epithelium and immune system – which makes perfect sense if you think about it![i]

They performed an analysis on samples of the inner mucus layer from 62 patients with IBS and compared them to samples from 31 healthy people.  The results were fascinating:  in 31% of those with IBS (especially those with diarrhea-predominant IBS, where it was found in 40% of individuals) they found a pathogenic bacterium called Brachyspira.  The did not find it in a single healthy control!  This bacterium would not be found in fecal samples:  it was only seen in the mucus biopsy.  They found that those with the infection have gut inflammation that resembles an allergic reaction:  there was an increase in immune cells, including eosinophils.  And total and activated mast cells (which release histamine) were significantly increased in those with the Brachyspira infection.  They also found that in those infected, the total mucus layer was reduced in thickness, making those individuals more prone to invasion by other bacteria.

The researchers state that their findings do need to be confirmed in a larger study but that this work does perhaps provide an opportunity to develop a cure of many who suffer from IBS, especially those with diarrhea-dominant type.  Says one of the scientists, “Brachyspira seemed to be taking refuge inside the intestinal goblet cells, which secrete mucus.  This appears to be a previously unknown way for bacteria to survive antibiotics, which could hopefully improve our understanding of other infections that are difficult to treat.”[ii]  In a pilot study, those with IBS and Brachyspira were treated with antibiotics and the doctors were able to eradicate the pathogen.  The authors suggest that in the future, probiotics and perhaps dietary changes may also be used for successful treatment.

Up to now, Brachyspira was not considered a major deal – in fact, it was mostly considered a commensal, meaning that it existed normally in us with no negative effect.  However, as they state in this article, what they found in those infected was not dissimilar to infection with salmonella and other major gut pathogens! They conclude by saying, “…our observations suggest Brachyspira as a potential human pathogen rather than merely a harmless commensal.”

One thing I’m puzzled about:  in looking up a little about Brachyspira, with which I was not familiar, I found that it is a common colonizer of pigs and chickens and causes disease in these animals.  It is also common in humans living in developing countries with poor sanitation.  However, it was already known that be pathogenic by 2018 when an article on it appeared in Clinical Microbiology Reviews:  “…it has been identified histologically attached to the colon and rectum in patients with conditions such as chronic diarrhea, rectal bleeding, and/or nonspecific abdominal discomfort…”  I wonder how those in the industrialized world would manage to pick it up!

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

[ii] https://www.nutraingredients.com/Article/2020/11/27/Research-uncovers-hidden-gut-bacteria-in-IBS-patients