Infants with low levels of "good" bacteria in their gut may have a higher risk of developing childhood asthma. | Flickr/ KristyFaith/ CC BY-NC-ND 2.0
Infants harboring low levels of four "good" bacteria in the gut are more likely to develop asthma later in life, according to a study of more than 300 children published in the 30 September issue of Science Translational Medicine.
The findings pave the way to identifying infants at high risk of asthma by screening microbes in their stool. They also suggest that a probiotic containing a mixture of the protective bugs may offer a therapeutic avenue for preventing asthma.
"Our longer-term vision would be that potentially children in early life could be supplemented with [a] flavor or some combination of flavor [of the bacteria] to look to prevent the ultimate development of asthma," said senior author Stuart Turvey, from the University of British Columbia (UBC) and British Columbia Children's Hospital, at a 29 September press teleconference.
But as Brett Finlay, also a senior author of the study from UBC, noted, "Commercialization will certainly take a few years."
Finlay, Turvey, and colleagues tracked 319 Canadian children from birth to three years of age. Using high-throughput genomic sequencing of stool samples and analyzing metabolites in feces and urine, the researchers surveyed their gut microbiota — the community of microbes that colonizes our gut — at three months and one year of age.
They found that three-month-old infants who harbored low levels of four types of bacteria — in the genera Lachnospira, Veillonella, Faecalibacterium, and Rothia — were more likely to be diagnosed with asthma by age three. Of the 319 children, 22 fell into this high-risk group, eight of whom have been diagnosed with asthma so far, according to Turvey.
The results point to a "critical window" early in life in which disruptions in the healthy development of the gut microbiome can lead to asthma.
"Our study I think emphasizes that in that first 100 days [of life], the structure of the gut microbiome seems to be very important in influencing the immune responses that cause or protect us from asthma," said Turvey.
The research team discusses the links between the immune system, gut bacteria, and children's asthma risk. | UBC
The number of asthma cases has risen dramatically in the past three decades. Today, asthma afflicts 300 million people worldwide, particularly in developed countries, and is the most common chronic disease in children.
Growing evidence suggests that the intestinal microbiome serves as a critical link between the environment and our immune system. Gut microbes are thought to communicate with mucus-lined surfaces of the body exposed to the environment, such as the mouth, nose, and lungs, said Finlay.
"What [the] data's really starting to show these days is that the immune system kind of gets itself set up in the gut and that influences how it then works everywhere else in the body," said Finlay.
Events and environments that perturb the gut microbiome have been associated with increased risk of asthma. These disturbances include early exposure to antibiotics, bottle-feeding instead of breastfeeding, Cesarean section compared to vaginal delivery, and even living in cities as opposed to farms.
"There's all these sort of smoking guns to indicate that the microbiota may be involved in this, but there were no experiments to prove it," said Finlay.
Little is known about the four bacteria, other than the fact that they are harmless, according to Marie-Claire Arrieta from UBC. "This is another example of how little we know about most of the microbes that inhabit us," she said.
To probe the bacteria's function, the researchers transferred feces from one of the high-risk children to adult germ-free mice. Restoring the four bacteria in these mice markedly reduced airway inflammation in their offspring, suggesting the bugs may have a therapeutic effect against asthma.
"Probiotics have [been] shown to be beneficial in a number of studies," said Leah Stiemsma from UBC and the Child & Family Research Institute. "We're currently working on…looking at how these bugs might be utilized as probiotics."