Female mice treated with two classes of widely used childhood antibiotics, in a new study, developed larger bones and gained more weight than untreated mice. Both antibiotic types also impaired the gut microbiome, the trillions of microbes that inhabit the intestinal tract.
The study, by NYU Langone Medical Center researchers, comes at a time of growing evidence that multiple courses of commonly used antibiotics may have a significant impact on children’s development.
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 simulate 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.
Microbiome Ecology Changed
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.
Senior author Martin Blaser, MD, director of the NYU Human Microbiome Program at NYU School of Medicine, notes 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.
The average child in the United States, he says, receives 10 courses of the drugs by the age of 10.
Based on thorough DNA sequencing data, the study demonstrated that both antibiotics also disrupted the gut microbiome.
“They changed the ecology of the microbiome in terms of the richness of the organisms, the diversity, and also what we call the community structure, or the nature of its composition,” Dr. Blaser says.
The medications changed not only the bacterial species, but also the relative numbers of microbial genes linked to specific metabolic functions.
Combined, the researchers say the more pronounced effects of tylosin on weight gain and microbiome disruption are particularly worrisome, given the increasing popularity of macrolide antibiotic prescriptions for children. The evidence, they stress, highlights the need for better awareness of the potential downsides of antibiotic overuse.
Yael R. Nobel, Laura M. Cox, Francis F. Kirigin, Nicholas A. Bokulich, Shingo Yamanishi, Isabel Teitler, Jennifer Chung, Jiho Sohn, Cecily M. Barber, David S. Goldfarb, Kartik Raju, Sahar Abubucker, Yanjiao Zhou, Victoria E. Ruiz, Huilin Li, Makedonka Mitreva, Alexander V. Alekseyenko, George M. Weinstock, Erica Sodergren & Martin J. Blaser Metabolic and metagenomic outcomes from early-life pulsed antibiotic treatment Nature Communications 6, Article number:7486 doi:10.1038/ncomms8486