TORONTO - Canadian researchers have discovered that babies at high risk of developing asthma may have low levels of four types of bacteria in their gastrointestinal tracts — and replacing those microbes might prevent the disease.
Asthma is a chronic inflammatory disease that clogs the airways with mucous, causing an affected person to cough, wheeze and have difficulty breathing. The disease kills roughly 250 Canadians each year, about 20 of them children.
The condition arises when the immune system — which develops early in life through interactions with bacteria and other microbes in the gut — goes awry and attacks lung and airway tissues, causing them to overreact to allergens like pet dander and other environmental triggers.
A research team led by University of British Columbia scientists identified four bacteria that appear to be involved with the development of asthma when deficient in numbers.
Dubbed FLVR — for Faecalibacterium, Lachnospira, Veillonella and Rothia — these bacteria are typically acquired by babies from the environment. They are among trillions of bugs that make up the human "microbiome" and are critical for keeping us healthy.
But factors such as being born via a C-section versus vaginal birth, having formula over breastfeeding, and taking bacteria-destroying antibiotics early in life can alter the makeup of so-called good bacteria in the digestive system.
"This research supports the hygiene hypothesis that we're making our environment too clean," said co-lead investigator Brett Finlay, a microbiologist at the University of British Columbia.
"It shows that gut bacteria play a role in asthma, but it is early in life when the baby's immune system is being established."
The researchers, whose findings appeared Wednesday in the journal Science Translational Medicine, made that determination after analyzing fecal samples from 319 children enrolled in the Canadian Healthy Infant Longitudinal Development (CHILD) study.
Analysis of stool samples taken at three months of age found that 22 babies shown by allergy testing to be at very high risk of asthma had decreased FLVR levels in their gut flora compared to children at little or no risk.
However, the researchers found fewer differences in FLVR levels among the children at one year of age, suggesting the first three months of life are a critical period for the gut microbiome to help train the immune system.
"This discovery gives us new potential ways to prevent this disease that is life-threatening for many children," said co-lead researcher Dr. Stuart Turvey, a pediatric immunologist at BC Children's Hospital.
"It shows there's a short — maybe 100-day — window for giving babies therapeutic interventions to protect against asthma."
One intervention could come in the form of a probiotic containing the FLVR bacteria, said Turvey, but he noted that current probiotic products sold in drug and health-food stores contain "a small handful of bacteria and certainly don't include this FLVR combination that we've identified."
"The big, ambitious goal would be to develop a preventive strategy for asthma by treating with the FLVR bacteria," he said Wednesday from Vancouver. "But I have to emphasize we're not there yet.
"Very little is known about these FLVR bacteria and we couldn't consider that until we're absolutely sure that it was safe for children."
Fecal and allergy testing also needs to be done in larger groups of children to confirm the findings, said the researchers, who have begun testing samples from 500 more babies enrolled in a larger Canadian study looking at the factors that lead to allergies and asthma.
"Right now we've looked at this Canadian group of children," Turvey said of the 319 in the initial study. "But is it true elsewhere? We've teamed up with a group from Ecuador and we're working with Australians and others to see if this FLVR deficiency that we've identified holds true in other populations living in other countries."
In an accompanying editorial, New York University microbiome specialists Martin Blaser and Maria Gloria Dominguez-Bello say the study "provides new pieces of the puzzle."
"Confirmation and extension of these findings should allow us to develop better approaches to prevention, including restoration of microbiota," they wrote.
Asthma affects about 300 million people worldwide, but ironically it is western countries — not poorer, developing countries — where prevalence rates have risen most dramatically since the 1950s.
The disease now affects up to 20 per cent of children in developed countries like Canada.
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