Toxic bacteria linked to cancer
A common bug is likely behind bowel cancer, Christchurch researchers say after a world-first finding.
A University of Otago Christchurch research team has found the common and usually helpful gut bug, bacteroides fragilis, is toxic in some people.
The toxic form can disrupt cells in the gut lining and foster cancer in the bowel. Research team head and bowel cancer surgeon Professor Frank Frizelle said the discovery could be used to screen people for the bug, and it could be used to develop a lifesaving vaccine. The research team also want to study the role of diet on the toxic form of the bacteroides fragilis.
The world first study tracked the progress of 150 people who had undergone a colonoscopy, a diagnostic procedure, to check for pre-cancerous polyps. DNA samples of the bowel were taken from the participants to see if they had bacteroides fragilis.
After 12-15 years, 79 per cent of patients with the bacteria in their gut had developed pre-cancerous lesions.
Frizelle described the finding as a ‘‘game-changer’’ as it provided a vital clue about what drives the cancer.
Bowel cancer is the third most common cancer worldwide with rates in highly industrialised and wealthy countries more than 25 times that of some Asian and African nations.
New Zealand has one of the highest rates per capita of bowel cancer in the world, with 1300 deaths each year.
Earlier research by the Christchurch team found rates of the disease had grown significantly among people under the age of 50 in the past 20 years.
Frizelle said genetic mutation was unlikely to explain the increased rates in a relatively short period and dietary changes were more likely.
While every person inherited their particular make up of gut bacteria from their mother at birth, diet and age had been proven to influence its health, Frizelle said.
‘‘Our gut microbiome is an individual, delicately-balanced community and there is a cause and effect scenario; if we change or eradicate one bacteria, it can have a negative effect on other parts of the microbiome.
‘‘So the challenge is working out how to mitigate the effects of the toxic form of bacteroides fragilis, without affecting the rest of the gut microenvironment.’’
The research team plan to explore if changes in diet could have a positive effect on the bugs in the gut.
‘‘The earlier you can catch a disease, the better the prognosis.
‘‘We want to 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,’’ Frizelle said.
*June is Bowel Cancer Awareness Month.