Abstract
Bifidobacteria are one of the most abundant bacterial groups in the infant gut microbiota and are closely associated with infant health and can potentially affect health in later life. However, the details regarding the source of bifidobacteria have yet to be completely elucidated. This study aimed to assess neonatal oral fluid (OF) as a transmission route for bifidobacteria to the infant gut during delivery. Neonatal OF and infant feces (IF) were collected immediately and one month after birth from 15 healthy vaginally delivered newborns. Bifidobacterium strains were isolated from OF and IF samples, and the similarity of strains between the OF-IF pairs was evaluated based on the average nucleotide identity (ANI) value. The 16S rRNA gene sequencing results revealed the presence of Bifidobacteriaceae at >1% relative abundance in all OF samples. Bifidobacterium strains were isolated from OF (9/15) and IF (11/15) samples, and those sharing high genomic homology (ANI values >99.5%) between the neonatal OF and IF samples were present in one-third of the OF-IF pairs. The results of this study indicate that viable bifidobacteria are present in neonatal OF and that OF at birth is a possible transmission route of bifidobacteria to the infant gut.
Highlights
The infant gut microbiota are crucial for infant health and may affect health status in later life[1,2]
These results suggest that human milk is a reservoir of bifidobacteria but raises the question of whether human milk is the initial source of microbes for infants
The precultivated oral fluid (OF) samples and those cultivated for 48 h were used to analyze the microbiotic profiles of the samples and to isolate Bifidobacterium strains
Summary
The infant gut microbiota are crucial for infant health and may affect health status in later life[1,2]. Several studies have been conducted on the transmission routes of bacteria, including bifidobacteria, and the development of infant gut microbiota, the details of this transmission remain unclear[7,8,9,10] The establishment of this microbial ecosystem occurs from birth and is influenced by various factors, such as type of infant feeding, birth mode, etc. Cesarean section (C-section) was shown to be associated with a lower abundance of bifidobacteria in the infant gut than was vaginal birth[7,9] These results suggest that the birth canal is an important source of maternal bacteria, including bifidobacteria, during the delivery process. We speculated that neonatal oral fluid (OF) at delivery is an important source of bacteria from both maternal and environmental ecosystems and may contribute to the early delivery of bacteria to the digestive tracts of neonates
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