Specific gut bacteria linked to irritable bowel syndrome

Researchers at the University of Gothenburg have detected a connection between Brachyspira, a genus of bacteria in the intestines, and irritable bowel syndrome (IBS) — especially the form that causes diarrhoea. There is hope that the discovery, published in the journal Gut, might lead to new remedies for many people with IBS, although larger studies will be required for confirmation.

Globally, between 5 and 10% of the adult population have symptoms compatible with IBS. The condition causes abdominal pain and diarrhoea, constipation or alternating bouts of diarrhoea and constipation. People with mild forms of IBS can often live a fairly normal life, but if the symptoms are more pronounced it may involve a severe deterioration in the quality of life.

The Gothenburg researchers hypothesised that IBS is caused by microbial imbalance, but analysis of faecal microbiota did not demonstrate consistent alterations. So the researchers instead took colonic tissue samples (biopsies) from 62 patients with IBS and 31 healthy controls, analysing bacterial proteins in mucus taken from the samples.

The study found that 19 of the 62 IBS patients (31%) had Brachyspira in their gut, while the bacteria was not found in any samples from the healthy volunteers. Brachyspira was particularly common in IBS patients with diarrhoea.

“Unlike most other gut bacteria, Brachyspira is in direct contact with the cells and covers their surface,” said Dr Karolina Sjöberg Jabbar, first author of the study. “I was immensely surprised when we kept finding Brachyspira in more and more IBS patients, but not in healthy individuals.”

“The study suggests that the bacterium may be found in about a third of individuals with IBS,” said study co-author Professor Magnus Simrén, also a Senior Consultant at Sahlgrenska University Hospital. “We want to see whether this can be confirmed in a larger study, and we’re also going to investigate whether, and how, Brachyspira causes symptoms in IBS. Our findings may open up completely new opportunities for treating and perhaps even curing some IBS patients, especially those who have diarrhoea.”

In a pilot study that involved treating IBS patients with Brachyspira with antibiotics, the researchers did not succeed in eradicating the bacteria. According to Dr Sjöberg Jabbar, “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.”

If the association between Brachyspira and IBS symptoms can be confirmed in more extensive studies, other antibiotic regimens, as well as probiotics, may become possible treatments in the future. Since the study shows that patients with the bacteria have a gut inflammation resembling an allergic reaction, allergy medications or dietary changes may be other potential treatment options. The researchers plan to investigate this in further studies.

“Many questions remain to be answered, but we are hopeful that we might have found a treatable cause of IBS in at least some patients,” Dr Sjöberg Jabbar said.

Image credit: ©stock.adobe.com/au/Andrey Popov

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