Background and aims Intrapartum antibiotic prophylaxis (IAP) is the most effective strategy to prevent early-onset Group B Streptococcal (GBS) sepsis. A possible role of IAP on neonatal microbiota is assumed. We aimed to evaluate the effect of IAP on the bacterial colonisation of neonatal gut at 7 and 30 days of life (DOL).

Methods Term newborns, vaginally delivered, were recruited at 2 DOL and allocated into four groups. Group 1: infants exclusively breastfed, not exposed to IAP. Group 2: infants partially breastfed (receiving at least 50% of own mother’s milk), not exposed to IAP. Group 3: infants exclusively breastfed, exposed to IAP. Group 4: infants partially breastfed, exposed to IAP. Faecal samples from the enrolled infants were collected at 7 and 30 DOL. The count of Bifidobacteriumspp., assessed by real-time PCR, was compared between the four groups.

Results Fifty-five newborns were recruited: 25 in Group 1, 7 in Group 2, 17 in Group 3, 6 in Group 4. On day 7, IAP-exposed newborns showed a significantly lower count of Bifidobacterium spp. (p < 0.05). Among infants not exposed to IAP, Bifidobacterium spp. count was significantly higher in Group 1 compared to Group 2. On day 30, a significant increase in Bifidobacterium spp. count (p < 0.05) compared to day 7 was observed in all groups.

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Abstract PS-187 Table

Conclusions Early neonatal microbiota is significantly affected by IAP, resulting in a reduced Bifidobacteria colonisation. Breastfeeding promotes the development of bifidogenic flora and possibly contributes to increase Bifidobacterium spp. count in IAP-exposed newborns ad 30 DOL.