DDW 2014 Note: Altered Balance of Bacteria in the Mouths of People With IBS.

Advances in technology and ever-decreasing cost of large-scale DNA analysis have made it possible in the past few years to conduct a census of the bacterial populations that live in different places inside individual human beings. A number of such studies have been done on IBS patients, and they are revealing that IBS patients may have an abnormal balance in their bacterial populations (more of certain bacteria types and less of others) compared to other people. This raises the possibility that such bacterial imbalance may be contributing to symptoms and, by extension, that these bacterial differences could be corrected to help improve IBS. And in fact, both treatment with probiotics (beneficial bacteria that are taken in capsules and are thought to restore balance in the bacterial population in the intestines) and treatment with antibiotics that mostly work within the bowel (neomycin and rifaximin) have shown clear positive effects on the symptoms of some IBS patients in multiple studies1,2. This provides indirect but persuasive evidence that bacteria play a definite role in IBS symptoms. However, much is still poorly understood about this phenomenon of bacterial abnormality in IBS. It is unclear, for example, which bacteria exactly are trouble-makers (apart from a couple of notorious offenders like Clostridium Difficile) or how they cause trouble.

The balance between different types of bacteria in IBS has typically been studied in stool samples, and that makes good sense since IBS is a bowel problem. But could bacterial imbalances also be present in other parts of the body in people with IBS? A study presented yesterday (Saturday May 3) at Digestive Disease Week 2014 in Chicago indicates that bacterial abnormalities are in fact present in the other end of the GI tract as well – in the mouths of IBS patients.

Fourie and colleagues at the National Institutes of Health in Bethesda, Maryland, collected samples of bacteria from the lining of the mouth cavity of 19 IBS patients and also from the same number of healthy controls who were matched to the IBS patients in height, weight, race and sex. They then ran whole microbiome DNA analysis on the samples to identify the types of bacteria present based on their genes, and then calculated how abundant different types of bacteria were in the mouths of IBS sufferers versus the healthy comparison subjects.

The team found that the people with IBS had significantly more of three bacteria types – Prevotellacea, Lachnospiraceae, and Rikenellaceae – compared to the healthy individuals. The latter two kinds of bacteria have already previously been found to be incresed in IBS according to the authors. The researchers further did some bowel stress test that involved swallowing a mixture of 4 types of sugars, and measured the stress hormone cortisol in the participants’ urine to evaluate the amount of stress response to this stimulation, and they discovered that the amount of Lachnospiraceae bacteria was related to the intensity of the body’s stress response to the sugar stress test. However, IBS patients (who had a higher concentration of that type of bacteria) had less stress response to the sugar stressor, so the meaning of that bacterial association is a bit ambiguous.

The significance of this study, even though it is small and the findings need to be replicated, is that it indicates that abnormal bacterial balance is probably not limited to the lower part of the GI tract in IBS, but is likely to be found all over in the GI tract – even in the parts furthest away from the small or large bowels where most biological and physiological investigations in IBS have been concentrated. As the authors suggest, sampling bacteria in the mouth could be a convenient way (compared to stool samples) to measure the microbe inbalances in IBS patients that could potentially be treated to improve their IBS symptoms.


Sa1185. Nicolaas H. Fourie, Dan Wang, Paul A. Smyser, Sarah Abey1, LeeAnne Sherwin, Bridgett Rahim-Williams, Wendy A. Henderson. Dysbiosis of the Mucosa-Adherent Microbiome in Patients With Irritable Bowel Syndrome. NINR & NIMHD, NIH DHHS, Bethesda, MD.


1. Ohman L, Simrén M. Intestinal microbiota and its role in irritable bowel syndrome (IBS). Curr Gastroenterol Rep. 2013 May;15(5):323. Review. PubMed PMID: 23580243
2. Cash BD. Emerging role of probiotics and antimicrobials in the management of irritable bowel syndrome. Curr Med Res Opin. 2014 Apr 14. [Epub ahead of print] PubMed PMID: 24666019


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