The impact of postnatal antibiotics on the preterm intestinal microbiome

BACKGROUND: Development of the intestinal microbiome in preterm infants has significant impact on infant health. Our objective was to determine if duration of antibiotics within the first 10 and 30 d after birth affects the intestinal microbiome. METHODS: Subjects were 24 0/7-31 6/7 wk of gestational age who received >= 50% breast milk and a total of 100 ml/kg of feeds by 10 d. Rectal (fecal) swabs were collected at 10 and 30 d and analyzed by 16S rRNA pyrosequencing. At both time points, we examined the rectal microbiome from infants who received only 2 d of antibiotics and those who received at least 7 d of antibiotics. RESULTS: In the 29 infants enrolled in our study, we found a decrease in diversity index from 10 d samples in those who received more antibiotics. Such difference in diversity and richness was not as pronounced in 30 d samples. Firmicutes and Bacteroidetes were most abundant in the 10 d samples. While these two phyla remained dominant in 30 d samples, there was an increase in Proteobacteria and Actinobacteria. CONCLUSION: Despite antibiotic therapy, neonates continued to acquire bacteria in the gastrointestinal tract. The process of bacterial acquisition is perturbed with the use of antibiotics.