A new animal study by NYU Langone Medical Center researchers adds to growing evidence that multiple courses of commonly used antibiotics may have a significant impact on children’s development. In the study, to be published online June 30 by the journal Nature Communications, female mice treated with two classes of widely used childhood antibiotics gained more weight and developed larger bones than untreated mice. Both of the antibiotics also disrupted the gut microbiome, the trillions of microbes that inhabit the intestinal tract.
Overall, the mice received three short courses of amoxicillin (a broad-spectrum antibiotic), tylosin (which isn’t used in children but represents another common antibiotic class called the macrolides, which is increasingly popular in pediatrics), or a mixture of both drugs. To mimic the effects of pediatric antibiotic use, the researchers gave the animals the same number of prescriptions and the same therapeutic dose that the average child receives in the first two years of life. A control group of mice received no drugs at all.
Martin Blaser, MD, the Muriel G. and George W. Singer Professor of Translational Medicine, director of the NYU Human Microbiome Program at NYU School of Medicine, and the study’s senior author, cautions that the study was limited to mice. Even so, he says the results agree with multiple other studies pointing toward significant effects on children exposed to antibiotics early in life, and he notes that the cumulative data could help shape guidelines governing the duration and type of pediatric prescriptions. “We have been using antibiotics as if there was no biological cost,” says Blaser. The average child in the United States, he says, receives 10 courses of the drugs by the age of 10.
The study supports previous research by Blaser’s group suggesting that antibiotic exposure during a critical window of early development disrupts the bacterial landscape of the gut and permanently reprograms the body’s metabolism, setting up a predisposition for obesity. The new study found that short, high-dose pulses of tylosin had the most pronounced and long-lasting effect on weight gain, while amoxicillin had the biggest effect on bone growth—a prerequisite for increased height.