Bacterial Vaginosis (BV) is a common condition involving a disruption in the natural balance of the vaginal microbiome. This imbalance occurs when protective bacteria are overtaken by other types of microorganisms. Because BV is often associated with sexual activity, questions arise about whether these bacteria can affect other parts of the body, particularly the mouth, or be transmitted through oral contact. This article examines the biological factors governing the oral and vaginal environments to determine the risk of BV-associated bacteria causing issues in the oral cavity.
Defining Bacterial Vaginosis and Its Causes
Bacterial Vaginosis is characterized by a significant shift in the vaginal microbial community structure, which is normally dominated by Lactobacillus species. These beneficial bacteria produce lactic acid, maintaining a protective, highly acidic environment in the vagina, typically at a pH of 4.5 or below. When this balance is disturbed, the concentration of Lactobacillus species decreases dramatically.
This reduction allows for the overgrowth of a diverse group of anaerobic bacteria. The condition is not caused by a single organism but by a complex change where certain bacteria thrive in the absence of protective Lactobacillus species. Key bacteria associated with this shift include Gardnerella vaginalis, Prevotella species, Mobiluncus species, and Atopobium vaginae.
The overgrowth of these anaerobic microorganisms results in the classic symptoms of BV, which are limited to the vaginal environment. These symptoms often include a thin, gray or white discharge and a characteristic “fishy” odor, caused by volatile organic compounds produced by the anaerobic bacteria.
Differences Between Oral and Vaginal Ecosystems
The human body contains many distinct microbial communities, and the environment of the mouth is fundamentally different from that of the vagina. These differences in ecological factors largely dictate which microorganisms can colonize and thrive in each location. The pH level is the most significant distinguishing factor between the two sites.
A healthy vagina maintains a distinctly acidic environment, with a pH typically ranging from 3.5 to 4.5. This low pH is a direct result of the lactic acid produced by the dominant Lactobacillus bacteria and actively inhibits the growth of most other organisms. In contrast, the healthy oral cavity is near neutral, with an average salivary pH typically falling between 6.7 and 7.3.
The oxygen availability also varies drastically between the two sites. The mouth is a mixed environment, containing areas exposed to high oxygen concentrations and other areas, like deep gum pockets, that are more anaerobic. Conversely, the vaginal environment is naturally low in oxygen, described as hypoxic.
The microbial diversity of the two environments is also vastly different. The oral cavity hosts a complex and highly diverse community of microorganisms, considered the second most diverse in the body. This contrasts with the healthy vaginal microbiome, which is characterized by very low diversity and dominance by one or two Lactobacillus species. These unique physical and chemical differences mean that bacteria adapted to one site are poorly equipped to colonize the other.
Assessing Oral Transmission and Infection Risk
The question of whether Bacterial Vaginosis can get in the mouth comes down to the successful colonization of BV-associated bacteria in the oral cavity. While BV-linked bacteria, such as Gardnerella vaginalis, can be transferred to the mouth through direct contact, the risk of a true infection or the development of “Oral BV” is low. There is currently no recognized medical condition defined as “Oral Bacterial Vaginosis.”
Any BV-associated microorganisms introduced to the mouth are generally transient passengers unable to establish a thriving, long-term colony. The neutral pH and higher oxygen availability in the oral environment are unfavorable conditions for the anaerobic bacteria that cause BV. These bacteria are adapted to the hypoxic conditions of the dysbiotic vagina. The body’s natural mechanisms, such as salivary flow and the highly competitive existing oral microbiome, work to eliminate these foreign microbes.
The primary concern regarding the oral-vaginal microbial connection is actually the reverse: the transfer of oral bacteria to the vagina. Certain bacteria commonly found in the mouth, like Fusobacterium nucleatum and Prevotella species, are known to be transmitted during oral-genital contact. When these oral species are introduced to the vagina, they can disrupt the existing Lactobacillus balance.
These oral microorganisms can contribute to the events that lead to BV by helping to create a hostile environment for the protective Lactobacillus species. For instance, Fusobacterium nucleatum can alter the vaginal environment, making it more hospitable for Gardnerella vaginalis to grow and form the characteristic BV biofilm. Therefore, while BV itself does not typically colonize the mouth, the oral microbiome can play a role in increasing the risk of BV in the vaginal environment.