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Toxic Form of Gut Bug Is Likely to Cause Bowel Cancer

Scientists at the University of Otago have identified a toxic microbe that may cause bowel cancer and lead to the development of a vaccine or early detection test.

Bacteroides fragilis is a common bacteria in our gut, and for the most part helps with digestion and the general health of the colon. However, in some people the bug produces a toxin that disrupts the cells that line the gut. The researchers found the toxic form of the bacteria in the gut of almost 80% of people with a pre-cancerous lesion – a precursor to the disease.

Bowel cancer is becoming increasingly common in people under the age of 50. This could be due to changes in our diet, which has a direct influence on our gut health and the microorganisms living there.

The researchers tracked the progress of 150 people who had undergone a colonoscopy. They genetically analysed the DNA of samples of bowel taken during the colonoscopies to see if Bacteroides fragilis was present. Between 12 and 15 years after the initial colonoscopy, 79% of patients with the toxic bacteria in their gut had developed low-grade dysplasia – a type of pre-cancer.

Prof Frank Frizelle, a bowel cancer surgeon who led the Otago team, describes the study findings as a “game-changer” that “gives us a clue as to what is actually driving the cancer, and in doing so, it gives us a possible means of being able to manage it.

“We want study this bug and its impact further with a view to using it as a way to identify people who are at the highest risk of developing the disease, before it takes hold,” he said.