In a study published in August by Nature Pediatric Research, researchers at the University of Rochester Medical Center investigated the development of preterm infants’ microbiomes after taking antibiotics.

Twenty-nine premature infants under antibiotic therapy were observed in the study. Of the 29, 27 were fed diets of mostly breast milk, and the other two were formula fed. Each infant was given antibiotics between 2 and 10 days, after which they had their microbiomes examined. Then, these infants were given new courses of antibiotics for the next 20 days, after which their microbiomes were examined again.

The study showed that the amount of antibiotics taken by the infants is directly associated with microbiome diversity. For example, after 10 days, the group that had been given 7-10 days of antibiotics had significantly less diversity in their gut microbiome than the group that only received 2 days of antibiotics. Over the next 20 days the microbiomes of each infant increased, however, suggesting that the gut continues to acquire new bacteria, and that diversity rebounds with time. In all cases, the microbiomes contained mostly bacteria from the firmicutes and bacteroidetes phyla, which is similar to normal infants. These results are important as they attempt to define the microbiome of preterm infants exposed to antibiotics, which is an important cohort of infants as they are most at risk for microbiome associated diseases like necrotizing enterocolitis (NEC).