Maternal Antimicrobial Use at Delivery Affects Gut Microbiota of Infants into the Early Weaning Period

Background: Intestinal colonization by bacteria such as Bifidobacterium or Bacteroides in infants and their presence in the gut at specific time points are known to affect the health of the host later in life. There are few published studies on the impact of maternal antimicrobial use at delivery on the gut microbiota in infants during the first year of life. To investigate the effect of antimicrobial administration immediately before delivery as intrapartum antibiotic prophylaxis (IAP) on the enteric environment in infancy around the weaning period and one year old.

Methods: A cross sectional study was conducted on healthy Japanese infants aged 6 months (n=23) and 12 months (n=26) to investigate the effect of antibiotic administration immediately before delivery as intrapartum antibiotic prophylaxis (IAP) on the enteric environment in infancy by using next generation sequencing to analyse the diversity and the composition of gut microbiota.

Results: In total, the fecal samples of 23 6-month-old and 26 12-month-old infants were analysed by next generation sequencing. Two 6-month-old infants and one 12-month- old infant were excluded because they had received antimicrobial drugs between birth and the sampling day. Antimicrobial agents were given systemically to the mothers at delivery for cesarean section, Group B Streptococcus-positive status, and premature rupture of membrane cases. IAP at the time of delivery does not influence the overall microbial diversity in the gut microbiota but decreased the occupancy by Bacteroides significantly (p=0.03), even in a subgroup analysis in infants group who were born by vaginal delivery at 6 months (p=0.02). In contrast, no influence of IAP was observed on gut microbiota in 12 months-old infants group.

Conclusion: Antimicrobial use immediately before the delivery are associated with decreased occupancy of Bacteroides in infants around weaning period. Although the current study provides a significant understanding of the gut microbiota in infancy, a follow-up study for a longer term is needed to identify the clinical significance of the change in the composition of gut microbiota based on the results.