Acquisition and establishment of the oral microbiota

Abstract

Acquisition and establishment of the oral microbiota occur in a dynamic process over various stages and involve close and continuous interactions with the host and its environment. In the present review, we discuss the stages of this process in chronological order. We start with the prenatal period and address the following questions: 'Is the fetus exposed to maternal microbiota during pregnancy?' and 'If so, what is the potential role of this exposure?' We comment on recent reports of finding bacterial DNA in placenta during pregnancies, and provide current views on the potential functions of prenatal microbial encounters. Next, we discuss the physiological adaptations that take place in the newborn during the birth process and the effect of this phase of life on the acquisition of the oral microbiota. Is it really just exposure to maternal vaginal microbes that results in the difference between vaginally and Cesarian section-born infants? Then, we review the postnatal phase, in which we focus on transmission of microbes, the intraoral niche specificity, the effects of the host behavior and environment, as well as the role of genetic background of the host on shaping the oral microbial ecosystem. We discuss the changes in oral microbiota during the transition from deciduous to permanent dentition and during puberty. We also address the finite knowledge on colonization of the oral cavity by microbes other than the bacterial component. Finally, we identify the main outstanding questions that limit our understanding of the acquisition and establishment of a healthy microbiome at an individual level.

Keywords: breastfeeding; delivery mode; infant; oral health; oral microbiota; plaque; puberty; saliva.

FIGURE 1

Interplay of factors contributing to acquisition and establishment of a personalized microbiome

FIGURE 2

Factors shaping the oral microbiota from fetus through childhood and toward adolescence

FIGURE 3

Hypothesis on the role of the placental microbiome in the development of fetal tolerance toward the (oral) microbiome of the mother, as proposed by Zaura et al ¹⁸ (Figure with permission from the authors)

FIGURE 4

Summary of hormonal, metabolic, immunologic, and other physiologic differences during the perinatal period, stratified according to mode of delivery. Factors in green are higher during vaginal delivery and those in blue are higher after Cesarian section, as discussed by Hyde et al, ²³ either in the mother or in the neonate. NEFA, nonesterified fatty acids; TSH, thyroid‐stimulating hormone

FIGURE 5

Niches in the infant oral cavity and their main microbial characteristics