Fungus in the gut may be a culprit behind Crohn’s disease

A fungus is a ‘key factor’ in the development of Crohn’s disease, a study has suggested.

Researchers say the findings, published in the journal mBio, could lead to new treatments for the debilitating inflammatory bowel disease, which causes abdominal pain, diarrhoea, weight loss and fatigue.

The study assessed the bacterial make-up of patients with Crohn’s disease, using healthy family members as control subjects. Researchers analysed faecal samples, and found strong fungal-bacterial interactions in those with Crohn’s disease.

Levels of two bacteria (Escherichia coli and Serratia marcescens) and one fungus (Candida tropicalis) were significantly higher in the sick family members, which suggests that the bacteria and fungus interact in the intestines.

This is the first time fungus has been linked to Crohn’s disease in humans.

Mahmoud Ghannoum, the study’s senior and corresponding author, said: ‘We already know that bacteria, in addition to genetic and dietary factors, play a major role in causing Crohn’s disease. Essentially, patients with Crohn’s have abnormal immune responses to these bacteria, which inhabit the intestines of all people.

‘While most researchers focus their investigations on these bacteria, few have examined the role of fungi, which are also present in everyone’s intestines. Our study adds significant new information to understanding why some people develop Crohn’s disease.

‘Equally important, it can result in a new generation of treatments, including medications and probiotics, which hold the potential for making qualitative and quantitative differences in the lives of people suffering from Crohn’s.’

Instant analysis
This prospective cohort paper shows that increased Candida tropicalis, a fungus commonly causing infection, may be implicated in the pathology of Crohn’s disease, insofar as it is found in higher amounts in the bowel of patients with Crohn’s as opposed to healthy patients. As always, we must remember that this is mere correlation and far from causation.

We are only now beginning to scratch the surface of the gut biome and its impact on human health but animal studies have suggested potentially spectacular effects on health when the biome is manipulated.

Crohn’s disease is a relapsing and remitting auto-immune condition. We understand how the disease develops but its cause, and much else, remains unknown. Treatment is generally with anti-inflammatories, steroids, immune modulators and other medications, none of which are side-effect free — hence the need to advance our understanding of the condition.

Sadly, there is more theoretical and anecdotal promise in Crohn’s disease in terms of potential disease manipulation than there is hard evidence.

For example, we do know that gut bacterial levels play a role. There is also preliminary evidence that a lower carbohydrate diet is associated with improved markers of the active disease state in children, but, while hundreds of online forums attest to the apparent efficacy of a low-carb diet, a gluten-free low-carb diet and other modifications, hard evidence in the form of clinical trials or even large cohort studies have not been done.

Take-home message: this is a valuable addition to our knowledge, but offers nothing that we can take action on just yet.
Research score: 3/5