Abnormal gut microbiota and IBD

Dr Paul Moayyedi is a professor in the Division of Gastroenterology at McMaster University, Richard Hunt/AstraZeneca Chair in Gastroenterology, and the inaugural assistant dean of research.

Is an abnormal gut microbiota a cause or consequence of inflammatory bowel disease?

Paul Moayyedi, BSc, MB ChB, PhD, MPH: As I mentioned in the lecture [see Fecal transplantation beyond C difficile], there are differences in the microbiota between those with ulcerative colitis, for example, and the healthy volunteers. Not all of those differences are real. It is just, if you test enough things enough times, you will see differences between 2 arbitrary groups. I think we need to do more studies to understand what the true differences are between those with ulcerative colitis and those that are healthy. Looking forward to when we get to that stage, I predict there will be differences and I predict most of those will be a consequence of the disease, not a cause of it. If you have diarrhea all the time, of course your microbiota are going to change.

However, I strongly believe that a few organisms will actually be causative for the disease and that this is an infectious disease for which we have not found the cause yet. I hope in the future we will. I am not sure that every case of Crohn disease or ulcerative colitis is caused by one organism; it probably is different organisms causing disease in different people, but in an individual this is one species, possibly even one strain of organism, that is driving the disease, rather than just general dysbiosis. I strongly believe that in inflammatory bowel disease this is driven by a single organism in a single person; not a single organism—rather a single type of organism in an individual person.