Composition and maternal origin of the neonatal oral cavity microbiota

Abstract

Background: The origin of the initial oral microbiota in neonates still remains poorly understood. Objective: The aim of this study was to understand how the maternal microbiota contributes to the initial neonatal oral microbiota. Design: Twelve mother-neonate pairs with samples from the maternal oral mucosa, uterine cervix and placenta and the neonatal oral cavity immediately after birth were studied. The microbiota composition and diversity were characterized by 16S rRNA gene sequencing (V3-V4 region). The microbiota analyses and comparisons were carried out with Calypso software version 8.1 and with SourceTracker 1.0.1. Results: Samples from the neonatal oral cavity showed moderately high bacterial diversity and low richness. The neonatal oral cavity microbiota seems to share features mainly with the microbes detected in the placenta, followed by the cervical microbiota and the maternal oral microbiota. No statistically significant differences in diversity (Shannon index, p = 0.14), richness (Chao1, p = 0.53) or in microbial composition were observed according to delivery mode. Conclusion: The neonatal oral cavity microbiota is not significantly modulated by the birth canal or maternal oral microbiota but displays clear associations with microbes in the placenta. These results suggest that the neonatal oral microbiota may have a prenatal origin.

Probiotic Supplementation during the Perinatal and Infant Period: Effects on gut Dysbiosis and Disease

“…The first colonizing bacteria enter the intestine through the oral cavity. In spite of some authors proposing that the birth canal microbiota is the most decisive modulator on infants' oral and gut microbiota, recent studies suggest that the microbiota of the oral cavity in the neonate might have a prenatal origin, preceding the birth canal exposure [33]. Although an imbalance in the birth canal can affect the neonate's oral microbiota.…”

Oral Microbiota and Cancer Development

“…Between individuals the microbiota composition varies according to age, sex, and diet in health and disease, in addition to geographical variations [13, 14]. The human microbiota starts to develop gradually before and after the delivery [15-17]. Most of these initial changes in the bacterial microbiota composition start to settle after some months of life, also in the oral cavity [18-28].…”

Evidence for contamination as the origin for bacteria found in human placenta rather than a microbiota

“…This dogma has been challenged by several publications suggesting the presence of bacteria in the fetal environment including inside the placenta [1][2][3][4][5][6][7]. Studies using combinations of quantitative PCR (qPCR), fluorescence in situ hybridization (FISH) and next-generation sequencing techniques propose the existence of a "placental microbiome" [1,2,[8][9][10][11][12][13][14][15][16][17][18]. More generally, bacterial species were found in placenta, amniotic fluid, fetal gut, meconium and the neonate's mouth, suggesting a microbial colonization of the fetus [1,15,19].…”

“…Studies using combinations of quantitative PCR (qPCR), fluorescence in situ hybridization (FISH) and next-generation sequencing techniques propose the existence of a "placental microbiome" [1,2,[8][9][10][11][12][13][14][15][16][17][18]. More generally, bacterial species were found in placenta, amniotic fluid, fetal gut, meconium and the neonate's mouth, suggesting a microbial colonization of the fetus [1,15,19]. Interestingly, reports indicated that variations in the bacterial composition of the "placental microbiome" were associated with pregnancy outcomes such as preterm birth, chorioamnionitis, macrosomia, gestational diabetes mellitus, excess gestational weight gain, low birth weight, and pre-eclampsia [2,8,9,11,17,18,[20][21][22][23].…”