Name: how infant oral microbes take hold
Uploaded: 2026-03-12T13:36:07.000Z
Duration: 1 min 28 s
Channel: JoVE

The fetal oral cavity is generally considered sterile, yet oral microbes like Streptococcus and Fusobacterium found in amniotic fluid indicate early exposure.The delivery mode significantly influences the initial oral microbiome.Vaginal birth introduces vaginal microbiota, while cesarean birth exposes the oral cavity of the newborn to skin microbiota.Oral microbial colonization begins within the first day after birth, as microbes from the surrounding environment, caregivers, and breast milk enter the oral cavity.Streptococcus salivarius is one of the pioneer species that colonize the oral mucosa.As the infant grows, other bacteria like Lactobacillus, Actinomyces, Neisseria, and Veillonella begin to colonize the infant&#8217;s mouth.Tooth eruption introduces new nonshedding surfaces that support microbial colonization of additional species, like Streptococcus mutans.The formation of gingival crevices enables colonization by periodontal microbes, increasing microbial diversity.These microbes adhere to the surfaces of teeth and to one another, forming biofilms that can develop into dental plaque.

development of the oral microbiota

Development of the Oral Microbiota

The establishment of the oral microbiome begins before birth, challenging the long-held belief that the fetal oral cavity is sterile. The presence of oral microbes such as Streptococcus and Fusobacterium in amniotic fluid suggests that microbial exposure may occur in utero, potentially through translocation from the maternal oral or gastrointestinal tract. This early colonization primes the neonatal immune system and sets the stage for subsequent microbial succession. Maternal health, particularly the presence of periodontal disease, may influence this prenatal microbial transmission.Delivery Mode and Microbial Transfer The mode of delivery is a critical determinant in shaping the initial composition of the infant's oral microbiota. Vaginally delivered infants acquire a microbiome rich in Lactobacillus and other constituents of maternal vaginal flora. In contrast, Cesarean-delivered infants are predominantly colonized by skin-associated microbiota such as Staphylococcus. These early differences may influence oral and systemic health outcomes later in life.Postnatal Microbial Succession Colonization of the oral cavity begins rapidly after birth, typically within 8 to 16 hours. This process is facilitated by microbial inputs from breast milk, maternal saliva, caregiver contact, and environmental sources. Streptococcus salivarius, a pioneer commensal, is among the first bacteria to establish on the oral mucosa, laying the groundwork for subsequent microbial communities. As the infant matures, additional genera such as Lactobacillus, Actinomyces, Neisseria, and Veillonella become prominent.Tooth Eruption and Gingival Development Tooth eruption introduces hard, nonshedding surfaces that favor the colonization of bacteria like Streptococcus mutans, a key contributor to dental caries. The emergence of gingival crevices further diversifies the oral microbiota by creating anaerobic niches suitable for periodontal pathogens. These microbes organize into complex, structured biofilms that adhere to dental surfaces and to each other. These biofilms play a dual role: they protect against pathogenic invasion while also contributing to oral disease under dysbiotic conditions.Understanding the development of the infant oral microbiome is crucial, as early microbial exposures have lasting impacts on immune maturation and overall health.

The establishment of the oral microbiome begins before birth, challenging the long-held belief that the fetal oral cavity is sterile. The presence of oral ...

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JoVE Core

Microbiology

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Human Microbiome and Virome

KEY TERMS AND CONCEPTS

how infant oral microbes take hold

Infant oral microbes begin to take hold before birth and continue to change after delivery. The oral cavity was once thought to be sterile in the fetus, but microbes such as Streptococcus and Fusobacterium have been found in amniotic fluid. This suggests that early microbial exposure may occur in utero through transfer from the maternal oral or gastrointestinal tract.

This prenatal exposure may help prime the newborn immune system. Maternal health can also matter, especially if the mother has periodontal disease, which may affect microbial transfer before birth. These early events help set the stage for later changes in the oral microbiome.

The mode of delivery strongly shapes the first oral bacteria an infant acquires. Vaginally delivered infants often receive Lactobacillus and other microbes linked to maternal vaginal flora. Cesarean-delivered infants are more often colonized by skin-associated bacteria such as Staphylococcus, and these early differences may affect oral and systemic health later in life.

After birth, colonization of the oral cavity begins quickly, usually within 8 to 16 hours. Breast milk, maternal saliva, caregiver contact, and environmental sources all help supply microbes. Streptococcus salivarius is one of the first pioneer commensals, and it helps establish the oral mucosal community.

As the infant grows, the oral microbiota becomes more varied. Genera such as Lactobacillus, Actinomyces, Neisseria, and Veillonella become more common. Tooth eruption then adds hard, nonshedding surfaces that favor bacteria like Streptococcus mutans, a major cause of dental caries.

Gingival crevices appear as the gums develop, and they create low-oxygen spaces for periodontal pathogens. The microbes in the mouth organize into structured biofilms that stick to teeth and to one another. These biofilms can help block invading pathogens, but under dysbiotic conditions they can also contribute to oral disease.

Understanding how the infant oral microbiome develops is important because early microbial exposure can influence immune maturation and overall health. The sequence from prenatal exposure to tooth eruption shows how the mouth becomes a changing microbial habitat. Each stage helps shape the community that forms during early life.

How Infant Oral Microbes Take Hold

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Infant oral microbes begin to take hold before birth and continue to change after delivery. The oral cavity was once thought to be sterile in the fetus, but microbes such as Streptococcus and Fusobacterium have been found in amniotic fluid. This suggests that early microbial exposure may occur in utero through transfer from the maternal oral or gastrointestinal tract. This prenatal exposure may help prime the newborn immune system. Maternal health can also matter, especially if the mother has...

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key terms and concepts

Learn how infant oral microbes first appear before birth, change after delivery, and shift again with tooth eruption and biofilm formation.

How Infant Oral Microbes Take Hold | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

How Infant Oral Microbes Take Hold

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