Baby's gut microbes may predict risk of asthma, allergies

Los Angeles: Scientists have identified microbes living in the guts of one-month-old babies that is linked to a three-fold higher risk of developing asthma and allergic later in childhood.

The discovery represents an opportunity to develop new treatments that could stave off allergies and asthma before they become established, said Susan Lynch, associate professor at University of California, San Francisco in the US.

"Currently, children are typically six or seven years old when they are diagnosed with asthma, which has no cure and has to be managed through medication," Lynch said.

The microbes living in a baby's gut during the first month of their life may impact the immune system, leading to a higher risk of allergies by the age of three and asthma by the age of four, scientists said.

Researchers, including those from the Henry Ford Health System in the US, showed that the perturbed microbial ecosystem present in these at-risk babies produces molecules that reduce the abundance of a key type of immune cell known to help prevent allergy.

They found that having fewer of these cells leads to a hyperactive immune system and eventually to chronic asthmatic inflammation of the lungs.

For the study, researchers collected stool samples from the diapers of the infants and kept them on ice.

Years later, they studied how soon after birth they could detect microbiome differences predictive of asthma later in life, and why these microbes were so influential in triggering the disease.

Researchers used high-throughput genetic analysis of the stool samples to map the gut microbes of 130 young infants around one-month of age.

This analysis, which was the first study of both bacterial and fungal diversity in the neonatal gut, found that the babies fell into one of three distinct groups, each characterised by different types of bacterial and fungal species in the gut.

Based on the team's two-year and four-year follow-up data, the smallest of these three groups (11 of 130 infants) were three times more likely to develop allergic diseases and asthma than the rest of the infants.

The size of this at-risk group was strikingly consistent with the rate of allergic asthma in the general population, Lynch said.

The microbial diversity analysis showed that these infants were missing certain normal gut bacteria and also that they possessed abnormally high levels of certain resident fungal species.

The researchers also examined a number of environmental and socioeconomic factors to learn why some children developed a high-risk gut microbiome profile.

They found that male infants were more likely to have the problem than females, and also that those who did not have dogs in the home were also more at risk.

The results appeared in the journal Nature Medicine.