Microbiome Vaginal: What It Is, Functions, Balance, and Tests

The vaginal microbiome is a topic of growing interest in medicine and scientific research due to its significance for women’s health. Understanding how the microbial community of the vagina influences immunity, nutrition, and overall well-being is crucial for doctors and specialists.  

   

This article explores the composition, functions, and relevance of the vaginal microbiome, highlighting its implications for reproductive health and disease prevention. 

 

The human body hosts a rich diversity of microorganisms, forming a dynamic, functional, and supportive system that develops in harmony with the physiological progress of its host. 

The human body hosts a rich diversity of microorganisms, forming a dynamic, functional, and supportive system that develops in harmony with the physiological progress of its host. 

 

Thus, microbiota plays a fundamental role in human physiological mechanisms, such as the development of immunity and nutrition, establishing a mutually beneficial relationship with the host, in which it provides shelter and nutrition. 

What Is the Vaginal Microbiome?

The vaginal microbiome is the collection of microorganisms, mainly bacteria, that naturally inhabit the vagina. These microorganisms form a living community, the vaginal flora, which functions in balance with the female body. 

 

Unlike the old idea that bacteria are always harmful, many of them are beneficial and essential for maintaining intimate health. 

 

Microbiota vs. Microbiome: What Is the Difference?

The term microbiota refers to the complex community of microorganisms that inhabit a specific location in the body, such as the gastrointestinal tract, skin, mouth, vagina, among others. 

 

The microbiota includes all bacteria, viruses, fungi, and other microorganisms that coexist in this environment, playing important roles in the health and functioning of the host organism. 

 

On the other hand, the term microbiome refers to the collective genome of a microbial consortium or community, meaning it is the complete set of genes of the microorganisms that form the microbiota (including the genetic material of all bacteria, viruses, fungi, and other microorganisms).  

 

Additionally, the term also refers to the activities and metabolic capabilities of the present microorganisms (1). 

 

The Importance of the Human Microbiome

In the early stages of life, the development of the microbiome influences immune function. Microorganisms acquired vertically, horizontally and through the environment, as well as their metabolic products, have the potential to shape developmental pathways that impact health throughout life (2). 

 

Thus, the microbiome plays a crucial role in the development of metabolic, immune and nutritional functions, necessitating careful attention.  

 

Understanding how complex microbial communities can affect the pathogenesis of various diseases has significant implications for their prevention, diagnosis, and treatment (3). 

 

In recent decades, the field of human microbiome research has evolved beyond merely cataloging the diversity of microorganisms, to understanding how these microorganisms constitute a dynamic and supportive functional system that develops synergistically, in parallel with the process of physiological development and decline (4-6). 

 

What is increasingly evident is that a wide range of conditions, including chronic inflammatory diseases (7), metabolic diseases (8), neurological disorders and cancer (9, 10), are now being linked to functional changes in the microbiome. 

 

These changes can occur both in isolation at the disease manifestation site and in mucosal areas or distant organ systems, triggering metabolic and immune changes in the host (1). 

 

Various factors, such as diet, antimicrobial agents and immunity, influence human microbiomes, especially the gut microbiome, which harbors the greatest quantity and variety of microorganisms.  

 

In response, bioactive products from the microbiome shape human cell function (11, 12). 

 

To better understand the influence of the gut microbiome on health, SYNLAB offers the MyBiome, a diagnostic test for the gut microbiome that performs a complete reading of the gut microbiome genome through massive sequencing (shotgun metagenomics).  

 

Read more about the intestinal microbiome and discover how MyBiome allows for an in-depth, objective, and actionable study of all the microorganisms that make up the intestinal ecosystem. 

 

 

Vaginal Microbiota and Microbiome

The vaginal microbiota constitutes about 9% of the total human microbiota (13) and is considered a dynamic microenvironment where pregnancy, contraceptive use, menstrual cycle, and sexual activity contribute to variations in bacterial communities (14, 15). 

 

The normal vaginal flora is believed to be dominated by lactobacilli. The species L. iners, L. crispatus, L. gasseri, and L. jensenii have been shown to predominate the vaginal microbiota of healthy women of reproductive age in varying proportions (16-18).  

 

About 120 species of Lactobacillus have been documented, and 20 are known to inhabit the vagina. 

 

However, an altered vaginal microbiota with a low abundance of lactobacilli, especially during pregnancy, can result in excessive inflammation and risk of premature birth (19, 20). 

 

Furthermore, since the vaginal microbiome plays an important role in embryo implantation, it is not surprising that bacterial vaginosis is more common in infertile women and is associated with reduced conception rates (13). 

 

These microorganisms live in a mutualistic relationship with the vagina, protecting it from potentially pathogenic microorganisms such as those causing bacterial vaginosis, urinary tract infections, Candida infections, and sexually transmitted infections (STIs) (21). 

 

This contribution appears to be indispensable for reproductive success. The microbiota acts as a frontline defender against invading microorganisms through a phenomenon called “colonization resistance,” preventing foreign organisms from colonizing areas of the human body and causing infections (22). 

 

The concept of a global pattern of normality versus vaginal microbiome dysbiosis is subject to debate, as women of different ethnicities have distinct vaginal microbiotas with regional variations (23). 

 

However, despite the great variability among women, it is currently accepted that the “healthy state of the vaginal microbiome” in women of reproductive age is characterized by the dominant presence of one or, at most, two species of Lactobacillus, with L. crispatus, L. iners, L. gasseri, and L. jensenii being the most common. 

 

Through the production of lactic acid, lactobacilli can maintain an acidic environment in the vagina which, along with the production of other antimicrobial compounds, helps inhibit or control the growth of opportunistic and pathogenic microorganisms. 

 

Normal Vaginal Microbiota

The normal vaginal microbiota is characterized by the predominance of protective bacteria, mainly from the genus Lactobacillus. These bacteria play a central role in defense against pathogenic microorganisms. 

 

Characteristics of normal vaginal microbiota: 

• Predominance of Lactobacillus (adheres to the vaginal epithelium, inhibiting the adhesion of pathogenic microorganisms);
• Production of lactic acid (through glycogen fermentation);
• Production of hydrogen peroxide (and other antimicrobial compounds, such as bacteriocins);
• Acidic environment (pH ≤ 4.5);
• Low bacterial diversity (unlike the intestine).

This acidic environment makes it difficult for opportunistic bacteria associated with infections to proliferate, as occurs in bacterial vaginosis. 

 

What Is the Normal Vaginal pH?

Vaginal pH indicates the level of acidity of the vaginal environment and is directly related to maintaining the balance of the vaginal microbiome and protection against infections. It functions as a “health marker” of the female intimate environment. 

 

Vaginal pH varies according to life stage and hormonal cycle:

• Women of reproductive age: 3.8 to 4.5; 
• During menstruation:it may temporarily increase; 
• Postmenopause: it tends to be above 4.5 due to decreasedestrogen; 
• Pre-puberty:higher pH (less acidic environment).

Estrogen stimulates glycogen production in vaginal cells, which serves as a substrate for Lactobacillus to produce lactic acid, maintaining an acidic and protective environment. 

 

The acidic environment makes it difficult for potentially pathogenic microorganisms to proliferate, such as: 

• Bacteria associated with bacterialvaginosis;
• Fungi of the genusCandida;
• Some bacteria related to sexually transmitted infections.

When the pH rises (becomes less acidic), natural protection decreases, favoring the growth of these microorganisms. 

 

What is Vaginal Dysbiosis?

The main constituents of the microbiome, bacteria, need to maintain constant symbiosis, which is the balance between commensal (beneficial) and pathogenic (harmful) bacteria. 

 

The opposite, known as dysbiosis, occurs when there is an imbalance in this relationship, triggering a pro-inflammatory microbiota pattern (3). Dysbiosis impairs health by increasing the host’s susceptibility to a spectrum of inflammatory and metabolic disorders (24). 

 

About 20-30% of women of reproductive age have an altered microbiome. Vaginal microbiota dysbiosis can be physiological or pathological, depending on the interaction of metabolic and microbial factors.  

 

The vaginal microbiota evolves with age, with anaerobic microorganisms being dominant in the prepubertal age, transitioning to a Lactobacillus-rich vagina in reproductive age (25). 

 

Imbalances in the vaginal microbiome are mainly caused by the depletion of Lactobacillus spp. Studies associate this decrease with an increased risk of sexually transmitted infections (STIs), as well as pregnancy complications (miscarriage and preterm birth) and less favorable in vitro fertilization outcomes (lower implantation rate and higher number of late miscarriages) (26, 27). 

 

Hormonal influence is also an important factor that determines the different phases of women’s reproductive cycles. Among the hormones, estrogens are known to induce specific modifications in the vaginal microbiota (28). 

 

Both physiological (pregnancy and menstrual cycle) and pathological (bacterial vaginosis, urinary tract infections, and sexually transmitted diseases) alterations are associated with significant changes in the vaginal microbiota (29). 

 

Therefore, in recent years, it has been recognized that the microbial community of the lower genital tract plays a fundamental role in maintaining women’s sexual and reproductive health. 

 

Difference Between Dysbiosis and Candidiasis

Dysbiosis refers to an imbalance of the vaginal microbiota, while candidiasis is an infection caused by excessive growth of fungi of the genus Candida. 

 

In other words, dysbiosis is an alteration of the vaginal ecosystem, while candidiasis is a possible consequence of this imbalance. 

 

Not every dysbiosis results in candidiasis, and not every case of candidiasis occurs exclusively due to dysbiosis, since hormonal, immunological, and metabolic factors also influence the development of infection. 

 

Another relevant point is vaginal pH: in bacterial vaginosis, which is a type of dysbiosis, pH is usually elevated. In candidiasis, pH often remains within the normal range, which helps in clinical differentiation. 

Relationship Between Vaginal Fungi and Flora Imbalance

Fungi such as Candida may be part of the vaginal microbiome without causing symptoms. The problem arises when the vaginal flora becomes imbalanced, with a reduction in protective bacteria and changes in the local immune environment.

 

This scenario allows excessive fungal proliferation, leading to the appearance of characteristic symptoms. Therefore, maintaining the balance of the vaginal microbiome is one of the main natural mechanisms for controlling vaginal fungi and preventing recurrent candidiasis.

 

Signs and Symptoms of Vaginal Dysbiosis

When an imbalance of the vaginal microbiome occurs, the body may present different signs. Changes in vaginal microbiota can cause a sensation of intimate discomfort, increased local sensitivity, inflammation, persistent discharge, or recurrent infections. 

 

Additionally, imbalance may increase susceptibility to sexually transmitted infections and other gynecological complications. 

 

The symptoms of vaginal dysbiosis vary depending on the type of alteration present and the intensity of the imbalance. In some cases, especially in early stages, a woman may not present obvious symptoms. 

 

When symptomatic, dysbiosis may cause:

• Vaginal discharge with color changes;
• Changes inconsistency;
• Stronger or unpleasant intimateodor;
• Burningsensation;
• Itching;
• Vulvarirritation;
• Discomfort during sexual intercourse.

In bacterial vaginosis, for example, discharge may become more fluid, grayish, and with a characteristic odor. In alterations associated with fungi, more intense itching and thick discharge may occur. 

 

These symptoms indicate that the vaginal microbiota may be imbalanced and that the intimate environment has lost part of its natural protection. 

 

However, it is important to remember that not every alteration in the vaginal microbiome causes immediate symptoms. Some women present subclinical dysbiosis, reinforcing the importance of seeking medical evaluation in cases of persistent discomfort or recurrent infections. 

 

Vaginal Microbiome and Infertility

The vaginal microbiome associated with bacterial vaginosis is believed to be a contributing factor to infertility in women of reproductive age (30). Women with idiopathic infertility show a higher incidence of abnormal vaginal microbiota (31). 

 

A systematic review study with meta-analysis on the association of bacterial vaginosis and infertility revealed that 19% of infertile women have bacterial vaginosis, while 39% had intermediate vaginal flora. 

 

Additionally, a higher prevalence of bacterial vaginosis was observed in infertile women compared to fertile women in the same age group, and this condition was related to reduced conception rates. 

 

These results reinforce the importance of the abundant presence of Lactobacillus species as a characteristic of healthy and normal vaginal flora (32). Therefore, a more comprehensive understanding of the functional elements, beyond the composition of the vaginal microbiome, can contribute to the improvement of diagnostic strategies and treatments. 

 

Gynecological Tests Related

The evaluation of female intimate health may involve different gynecological tests, each with specific purposes. While some focus on the prevention of cervical cancer, others help identify infections and changes in the vaginal microbiota. 

 

The main tests related to vaginal microbiome balance include: 

• Gynecological clinical exam: Physical evaluation performed toobserve signs of inflammation, discharge, odor, or anatomical changes; 
• Pap smear (oncotic cytology):Analyzes cervical cells and may indicate cellular alterations and the presence of microorganisms; 
• Conventional microbiological tests:Culture for bacteria or fungi, used when there is suspicion of a specific infection; 
• Vaginal microbiome test by molecular methods:A more detailed evaluation of the vaginal microbiota composition, allowing identification of balance patterns or dysbiosis. 

 

Treatment and Care

Treatment of vaginal dysbiosis depends on the cause of the imbalance and the symptoms presented. 

 

Since dysbiosis is not an isolated disease but rather a change in the vaginal microbiome, the main objective is to restore the balance of the vaginal microbiota and recover the vagina’s natural protective environment. 

 

Management may include antifungal medications, specific antibiotics (when bacterial vaginosis is present), adjustment of hormonal factors, and lifestyle changes that favor vaginal microbiome stability. 

 

To restore the balance of the vaginal microbiota, it is essential to identify the cause of the imbalance. Among the most commonly used strategies are:

• Targeted treatment for bacterial or fungal infections; 
• Guided use ofprobiotics;
• Reduction of irritative factors (vaginal douching, aggressive intimate soaps);
• Control of conditions such asdiabetes;
• Hormonal adjustments whenindicated.

It is also important to restore the vaginal microbiome, promoting the growth of protective bacteria such as Lactobacillus. In recurrent cases, a broader approach may be necessary, including metabolic, hormonal, and immunological investigation. 

 

How Do Probiotics Help the Vaginal Microbiome?

Probiotics can contribute to the balance of the vaginal microbiota by replenishing beneficial bacteria, especially Lactobacillus species. 

 

These microorganisms help with: 

• Production of lacticacid;
• Maintenance of acidic vaginalpH;
• Inhibition of pathogenic bacteria and fungigrowth;
• Stimulation of the local immune response.

Probiotics can be administered orally or vaginally, depending on the indication. However, their selection should be individualized, as different strains have specific functions. 

 

Which Test Does SYNLAB Offer for Investigating the Vaginal Microbiome?

SYNLAB offers a metagenomic study of the vaginal microbiome, allowing for the analysis of the relative abundance of bacterial species that make up the vaginal microbial community through shotgun metagenomic sequencing (complete bacterial genome sequencing). 

 

This approach avoids the amplification bias inherent in conventional studies based on 16S rRNA analysis and provides more precise species-level information. 

 

Additionally, the test includes RT-PCR analysis for infections by Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis, Mycoplasma genitalium/hominis, Ureaplasma urealyticum/parvum, and the following seven Candida species: C. albicans, C. glabrata, C. parapsilosis, C. krusei, C. dubliniensis, C. tropicalis and C. lusitaniae. 

 

What Are the Advantages of the Metagenomic Study of the Vaginal Microbiome?

The metagenomic study of the vaginal microbiome offers a comprehensive view of the vaginal microbiome, allowing for: 

• Characterization of the patient’s community state type (CST);
• Objective establishment of different dysbiosis states by using cut-off points validated in clinical studies;
• Precise characterization of the causal agents of infections, contributing to the optimization of the therapeutic approach for frequent vaginal tract infections.

A results report specifically designed to ensure quick and easy interpretation. 

 

What Are the Indications for the Metagenomic Study of the Vaginal Microbiome?

This study is especially indicated for women who: 

• Have infertility issues (recurrent implantation failure, repeated miscarriages);
• Patients suffering from recurrent vaginal infections (bacterial vaginosis, Candida spp, among others);
• Patients with chronic pelvic pain;
• Patients considering motherhood and/or wish to proactively assess their vaginal health. 

 

What Is the Methodology of the Metagenomic Study of the Vaginal Microbiome?

The metagenomic study of the vaginal microbiome is performed through shotgun sequencing, which involves the random fragmentation of small DNA fragments that are then sequenced individually. 

 

Shotgun sequencing is an effective approach for sequencing entire genomes, especially for organisms whose genomes are too large to be sequenced traditionally.  

 

This method allows the complete study of the genomes of all bacteria and microorganisms that make up the vaginal ecosystem. 

 

This approach avoids the amplification bias inherent in conventional 16S ribosomal gene studies, which often focus on only a small portion (less than 20%) of the 16S rRNA gene (33). 

 

Shotgun sequencing provides comprehensive information about an organism’s genome, enabling the analysis of genes, metabolic pathways, and regulatory elements, since the entire genome, including millions to billions of base pairs, is sequenced. 

 

In contrast, 16S gene sequencing is employed only to identify and classify bacteria present in a sample, it sequences only a specific region of the 16S rRNA gene, which is relatively short (about 1,500 bases) (33). 

 

Get to Know the SYNLAB Group, a Reference in Medical Diagnostic Services!

Performing precise and up-to-date tests is essential for making more accurate diagnoses and better directing treatments. SYNLAB is here to help you. 

 

We offer diagnostic solutions with rigorous quality control to the companies, patients, and doctors we serve. We have been operating in Brazil for over 10 years, working in 36 countries and three continents, and we are leaders in service provision in Europe. 

 

Contact the SYNLAB team and learn about the available tests. 

 

Frequently Asked Questions (FAQ)

What is the difference between microbiota and microbiome?

Microbiota is the set of microorganisms that live in a specific location in the body, such as the vagina. Microbiome refers to this set of microorganisms together with their genes and the interactions they exert in the environment. 

 

Simply put: microbiota are the microorganisms; the microbiome is the complete ecosystem. 

 

What is the concept of microbiome?

The microbiome is the set of microorganisms that inhabit the human body, together with their genetic material and biological functions. In the case of the vaginal microbiome, it represents the ecosystem responsible for maintaining balance, protecting against infections, and regulating vaginal pH. 

 

What is a microbiome test?

A vaginal microbiome test is a laboratory test that analyzes the composition of bacteria present in the vagina, usually through molecular methods. It allows the identification of vaginal microbiota imbalances and investigation of cases of dysbiosis or recurrent infections. 

 

What are the symptoms of dysbiosis?

Symptoms of vaginal dysbiosis may include: altered discharge, strong vaginal odor, burning sensation, itching, intimate irritation, and recurrent infections. In some cases, dysbiosis may be asymptomatic. 

 

What is good for curing dysbiosis?

Treatment depends on the cause. It may involve antifungals, specific antibiotics, probiotics, and lifestyle changes. The goal is to restore the balance of the vaginal microbiome and recover the protective acidic pH. 

 

Which type of test detects dysbiosis?

Dysbiosis may be suggested by clinical evaluation, vaginal pH measurement, and Pap smear. However, the vaginal microbiome test by molecular methods is the most precise for evaluating vaginal microbiota composition. 

 

What should people with dysbiosis avoid eating?

There is no absolute restriction, but it is recommended to reduce: refined sugar, excessive sweets, ultra-processed foods, and highly refined carbohydrates. These foods may favor fungal growth in cases of dysbiosis. 

 

How can vaginal pH be restored?

To restore vaginal pH, it is necessary to reestablish the balance of the vaginal microbiota. Avoiding internal douching, using gentle products, properly treating infections, and using probiotics when indicated may help normalize the vaginal environment. 

 

What is the relationship between nutrition and vaginal dysbiosis?

Diet influences the immune system and may indirectly impact the vaginal microbiome. Diets rich in sugar and ultra-processed foods may favor imbalances, while a balanced diet contributes to microbiota stability. 

 

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