DEVELOPMENT OF INTESTINAL FLORA IN BREASTFED NEWBORNS EXPOSED TO INTRAPARTUM ANTIBIOTIC PROPHYLAXIS

Objective:Intrapartum antibiotic prophylaxis (IAP) currently represents the most effective strategy to prevent the early-onset Group B Streptococcus (GBS) neonatal disease. We aimed to investigate the effect of IAP on the development of gut microbiota in breastfed term infants. Methods:Term newborns, vaginally delivered and receiving ≥50% of own mother’s milk, were recruited on day 2 of life and allocated into two groups. Group 1: infants born to mothers with GBS-positive vaginal swab, IAP-exposed. Group 2: infants born to mothers with GBS-negative vaginal swab, unexposed to IAP. Two fecal samples for each infant were collected on day 7 and 30.Bifidobacteriumspp.,Bacteroides fragilisgroup andLactobacillusspp. counts were detected by real-time PCR and compared between the two groups. Results: Seventy-six newborns were recruited (Group 1 = 41, Group 2 = 35). On day 7 (Table 1), the count ofBifidobacteriumspp. was significantly lower in Group 1 compared to Group 2 (p< 0.05), while no difference was detected on day 30 (Table 2). Consistently, Group 1 showed a significant increase inBifidobacteriumspp. count on day 30 compared to day 7 (p< 0.05). No differences were detected on days 7 and 30 between Group 1 and 2 in the number ofBacteroides fragilisgroup andLactobacillusspp. Conclusions:IAP affects the early neonatal microbiota by reducing Bifidobacteriumspp. levels. Breastfeeding, which promotes Bifidobacteriumspp. colonization, might be assumed to increase Bifidobacteriumspp. count in IAP-exposed newborns on day 30. Further studies are needed to evaluate the effect of different feeding modalities (e.g. formula feeding) on gut flora development in IAP-exposed newborns.