Treating preterm infants with antibiotics for more than 20 months appears to promote the development of multidrug-resistant gut bacteria, suggests a study funded by the National Institutes of Health. The research appears in Nature Microbiology.

Researchers used high-speed DNA sequencing and advanced computational analysis to study stool samples from 32 infants born very preterm who received antibiotic treatment for 21 months (in the neonatal intensive care unit and after discharge), nine infants born very preterm who received antibiotics for less than a week, and 17 healthy term and late preterm infants who hadn’t received antibiotics. Infants who received prolonged antibiotic treatment had less diverse bacterial populations in their gut, compared to the other infants, and these bacteria contained more antibiotic resistance genes.