TORONTO — Canadian researchers have discovered that babies at high risk of developing asthma 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 condition arises when the immune system -- which develops early in life through interactions with bacteria and other microbes in the gut -- overreacts to allergens 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 present in insufficient numbers.
Dubbed FLVR -- for Faecalibacterium, Lachnospira, Veillonella and Rothia -- these bugs are typically acquired by babies from the environment.
But factors such as being born via a C-section versus vaginal birth, having formula over breastfeeding, and antibiotic use early in life can alter the makeup of "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 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 high risk of asthma had decreased FLVR levels in their gut flora compared to children at low 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 a baby's developing 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 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 longer-term goal would be to see if we could offer ... those specific bacteria."
However, fecal and allergy testing needs to be done in larger groups of children to confirm the findings, and a commercialized probiotic is likely a few years off, the researchers said.
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.
The study was published Wednesday in the journal Science Translational Medicine.