Researchers identify bacteria linked with changes in gut microbiome of infants

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Events at birth may affect the microbes living in a baby's gut during the first few months of life, leading to a higher risk of childhood obesity and allergies, according to a new study published in the journal Gastroenterology.

For the study, the researchers used data from the CHILD Cohort Study (CHILD) to look at the complex relationships between birth events, a baby's gut microbiome at three and 12 months of age, and health outcomes at ages one and three.

To conduct the study, the researchers collected stool samples from the diapers of 1,667 infants who are part of CHILD, a national birth cohort study following nearly 3,500 Canadian children from before birth to adolescence with the goal of discovering the root causes of allergies, asthma, obesity, and other chronic diseases. They then analyzed the samples for gut microbes and their metabolites.

At one and three years of age, the children underwent skin prick tests to check for allergic sensitization to 10 common allergens.

The researchers linked factors such as caesarean section delivery and prolonged labor to changes in the gut microbes of infants. They then determined the pathways by which these alterations may lead to an increased risk of allergies and obesity later in childhood.

The study showed that infants born by caesarean section were more likely to have a high body-mass index score at ages one and three. When the researchers examined the children's microbiome profiles at three months of age, they found that an altered ratio of two types of bacteria, Enterobacteriaceae and Bacteroide, was the dominant path to overweight, according to the study.

At 12 months of age, a higher Enterobacteriaceae/Bacteroidaceae (E/B) ratio and colonization with Clostridioides difficile (C. difficile) were the main pathways leading to allergic sensitization.

"The takeaway from our study is that exposures at birth can trigger multiple and common gut microbial pathways leading to child overweight and allergic sensitization," said  Anita Kozyrskyj, BScPhm, MSc, PhD, senior author of the study and professor in the Faculty of Medicine & Dentistry at the University of Alberta, in a statement. "We may want to take steps to avoid unnecessary caesarean section deliveries, and possibly consider postnatal microbiota solutions that may help to prevent these two conditions."