Scientists have found evidence that antibiotics may have unintended effects on babies

Healthy microbes, healthy kid.
Healthy microbes, healthy kid.
Image: Reuters/Kai Pfaffenbach
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While babies learn to walk and talk, there’s another crucial piece of development taking place: the microbiome.

This collection of bacteria in our gut plays a crucial role in the way we break down food, put up defenses against pathogens, and even how we feel. Less robust microbiomes have been associated with obesity, allergies, inflammatory bowel diseases, and diabetes. In order to develop a strong microbiome, young children need to be exposed to diverse bacteria, which happens means primarily through mothers, other caretakers, and food.

Today (June 15) researchers from institutions including NYU Langone Medical Center and the Broad Institute of MIT and Harvard published two papers (paywall) in Science Translational Medicine that found the way a child is born, the types of food she’s given, and antibiotic treatments all affect the way her microbiome develops.

In general, more exposure to a mother’s microbes—either through vaginal birth or breast feeding—meant kids had more robust microbiomes. Antibiotic treatments, on the other hand, were found to have negative effects on children’s microbial populations.

“Exposing kids to unnecessary antibiotics decreases complexity, stability, and richness of the microbiome,” Ramnik Xavier, a microbiologist at the Broad Institute of MIT and Harvard and lead author of one of the papers, said. Xavier and his team found that after children were given rounds of antibiotics (usually for common ailments like ear or upper respiratory infections), children’s gut microbial population decreased, which is to be expected. However, they also found that immediately after treatment, populations of microbes with genes making them resistant to antibiotic treatments quickly spiked before decreasing to normal levels again. Although these types of resistant bacteria weren’t making the children sick at the time, they are much more difficult to treat if they wind up causing an infection.

For each of these papers, researchers took stool samples from about 40 children from when they were born until they were two and three years old respectively. They collected data about the children’s and their mothers’ health, and compared the ways in which these samples changed over time based on these different types of exposures.

To be sure, gut microbial health doesn’t necessarily reflect health consequences down the line. Researchers didn’t follow the children after the studies ended to see how they are currently doing, and there have been links, but not causality, between less diverse microbiomes and conditions like obesity, inflammatory diseases, and diabetes.

Sometimes, antibiotics are necessary for a child’s health. If a child has a bacterial infection that she can’t fight off with her immune system alone, antibiotics can help her recover relatively quickly. However, Xavier explained that in most cases, ear infections and common colds are caused by viruses; antibiotics don’t do any good, and end up wiping out some of the microbial populations necessary to maintain immune and gut health. Fortunately, relatively simple tests can show doctors whether or not harmful bacteria are to blame for a given infection.

In order to make sure your child’s microbial community stays healthy, Blaser recommended using antibiotics “only when necessary, as recommended by your doctor.” He also suggested avoiding antibacterial soaps and lotions. Although having robust gut microbes isn’t a guarantee for perfect heath, it can’t hurt to try to keep microbial populations thriving and diverse.