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Could your gut microbes be causing asthma?

Asthma was once a rare disease. Now it’s the most common chronic paediatric disease in the world and a leading cause for hospitalization of kids in Canada.

“This change happened in a short two-generation time period and it’s not because we evolved in this time. That kind of change takes hundreds of generations. We’ve done something to our world,” said Dr. Brett Finlay, professor of microbiology and author of the book, Let Them Eat Dirt.

Asthma is traditionally thought to be caused by a combination of environmental and genetic factors, but the emerging field of microbiome research offers an alternative explanation.

The human microbiome is the collection of all the microbes, like bacteria and fungi, living in and on our bodies. These near-invisible specs of life help digest our food, break down chemicals, dictate how we develop, influence our immune responses and much more.

When humans discovered in the late 1920s that penicillin could kill infection-causing microbes, an antibiotic-fueled campaign against bacteria ensued. The decrease in infectious diseases heralded by the antibiotic era was paired with a rise in immune disorders such as diabetes, inflammatory bowel disease and asthma.

“We see much higher rates of asthma among those who take antibiotics in the first year of life,” said Finlay. “What do antibiotics do? They affect microbes.”

Last year, Finlay and his colleagues discovered that when four particular bacteria were present in the guts of infants, their chance of developing asthma later in life went down. Infants without the four bacteria were more likely to develop asthma.

This discovery led Finlay and his team to run a similar study in rural Ecuador to see if these gut bacteria were also associated with asthma, which they found to be the case.

What surprised Finlay was that the presence of a different gut microbe — a yeast called Pichia — seemed to increase the chance a child would develop asthma. Finlay says his team was not specifically looking for Pichia. New lab techniques mean researchers can now easily identify fungi as well as bacteria in the microbiome.

“What we found doesn’t prove Pichia is causing disease, but there’s an association,” said Finlay. His next steps will be to test Canadian children’s gut microbiota for Pichia and to figure out its connection to asthma.

“One of the key roles of microbes early in life is to help our immune systems develop normally.” Finlay suspects Pichia interacts with the immune system since asthma involves inflammation of the airways.

“We can use inhalers and pills to prevent asthmatic attacks and we can try to limit environmental triggers, but we can’t prevent people from getting it,” said Finlay. Development of microbiome-related personalized medicine, like asthma screening or treatment in the first months of life, may be more feasible than other emerging tools like gene therapy.

“I like to tell geneticists they’re barking up the wrong tree. Humans are 99 per cent genetically identical, which makes finding and treating genetic diseases extremely challenging. When you consider all of your body’s microbes, there’s so much more to work with.”