The presence of four types of gut bacteria in infancy may reduce a child's risk for asthma, Canadian researchers report.
Most infants get these bacteria naturally from the environment. But some babies are given antibiotics that kill these bacteria, and some are not exposed to them for various reasons, the researchers said.
"We now have particular markers that seem to predict asthma later in life," lead researcher Brett Finlay, a professor of microbiology and immunology at the University of British Columbia in Vancouver, said during a news conference Tuesday.
"These findings indicate that bacteria that live in and on us may have a role in asthma," he said. This seems to happen by 3 months of age in ways that still aren't clear.
Coming into contact with environmental bacteria, such as by living on a farm or having pets, appears to decrease asthma risk, Finlay said.
Asthma, which has increased dramatically since the 1950s, affects up to 20 percent of children in western countries, according to the researchers. "Ironically, it has not increased in developing countries," Finlay said.
It's possible that people in these less-developed countries are exposed to more helpful bacteria and other microbes, he said. This is the so-called "hygiene hypothesis," which says environments that are too clean may actually impede development of the immune system.
The new report was published Sept. 30 online in the journal Science Translational Medicine.
For the study, Finlay and colleagues looked for four types of bacteria in stool samples of 319 infants at 3 months of age. The bacteria are called FLVR (Faecalibacterium, Lachnospira, Veillonella and Rothia).
The researchers found that 22 children with low levels of these bacteria at age 3 months also had low levels at age 1 year.
These 22 children are at the highest risk of developing asthma, and eight have been diagnosed with the respiratory disease so far, the researchers said.
Study co-author Dr. Stuart Turvey, professor of pediatric immunology at the University of British Columbia, said at the news conference that it's "not surprising how important early life is."
In the first 100 days of life, gut makeup influences the immune response that causes or protects kids from asthma, he said.
Testing for these bacteria in infants might help identify children who have a high risk of developing asthma, Turvey said. "These children could be followed and treated more quickly if they end up with asthma," he said.
While the study found a connection between gut bacteria and asthma risk in children, it did not prove cause and effect.
Whether giving kids probiotics -- good bacteria -- might reduce asthma risk isn't known, the researchers said. Turvey said the probiotics available in over-the-counter forms do not include the four bacteria identified in this study.
"Studies like ours are identifying specific bacteria combinations that seem to be missing in the children at the highest risk of asthma," he said. "The long-term goal is to see if we could offer these bacteria back, not the general nonspecific probiotics."
Finlay said these findings need to be replicated in larger groups and in different populations. He said the researchers also want to know if all four bacteria are protective, or just one or two.
"There could be other microbes that have a similar function, but we don't know that yet," Finlay said.
Turvey cautioned that treatment with bacteria is a long way off. "We are not ready for that yet," he said. "We know very little about these bacteria, but we are working to see if that might be a safe option to prevent this disease."
Dr. Maria Franco, a pediatric pulmonologist at Nicklaus Children's Hospital in Miami, had this to say: "The finding shows how our immune system in the first three months actually changes things in life for the long term."
It's still not known how these bacteria get into the gut, Franco said. "But it shows how something so natural can make a big difference in a child's life," she said.