RESUMEN
OBJECTIVES: To assess the establishment of the intestinal microbiota in very low birthweight preterm infants and to evaluate the impact of perinatal factors, such as delivery mode and perinatal antibiotics. STUDY DESIGN: We used 16S ribosomal RNA gene sequence-based microbiota analysis and quantitative polymerase chain reaction to evaluate the establishment of the intestinal microbiota. We also evaluated factors affecting the microbiota, during the first 3 months of life in preterm infants (n = 27) compared with full-term babies (n = 13). RESULTS: Immaturity affects the microbiota as indicated by a reduced percentage of the family Bacteroidaceae during the first months of life and by a higher initial percentage of Lactobacillaceae in preterm infants compared with full term infants. Perinatal antibiotics, including intrapartum antimicrobial prophylaxis, affects the gut microbiota, as indicated by increased Enterobacteriaceae family organisms in the infants. CONCLUSIONS: Prematurity and perinatal antibiotic administration strongly affect the initial establishment of microbiota with potential consequences for later health.