Women's Health, Bacterial Vaginosis, Vaginal Microbiome

Gardnerella Explained: What It Means for BV, Vaginal Dysbiosis & Recurrent Symptoms

“You've been told your vaginal swab showed Gardnerella. But what does that actually mean?”

Gardnerella is one of the bacteria most strongly associated with bacterial vaginosis (BV) — but finding Gardnerella on a vaginal test does not automatically mean you have BV.

That distinction matters.

Gardnerella can be detected in women without bacterial vaginosis, while BV itself is a polymicrobial vaginal dysbiosis involving changes across the vaginal microbial community rather than simply an infection with one bacterium. Different Gardnerella species may also have different biological characteristics and associations with BV.

For women experiencing recurrent BV, vaginal odour, discharge or symptoms that repeatedly return after treatment, understanding Gardnerella as part of the whole vaginal ecosystem can make much more sense than thinking of it simply as a “bad bacterium” that needs to be eliminated.

What Is Gardnerella?

Gardnerella is a genus of bacteria found within the human vaginal microbiome.

Historically, most discussion centred on Gardnerella vaginalis. We now know the Gardnerella genus is considerably more diverse, with multiple named species and additional genomically distinct groups identified.

These organisms do not all appear to behave identically.

Research suggests differences in characteristics such as adhesion, biofilm formation, enzyme activity and other potential virulence factors. This may help explain an observation that has puzzled researchers for years:

Gardnerella can be found in women with BV — but it can also be found in women without BV.

Recent research has also found that multiple Gardnerella species may coexist and that greater abundance and diversity of Gardnerella species are associated with BV.

So a laboratory report saying simply:

“Gardnerella detected”

doesn't tell us the entire story.

Where Does Gardnerella Fit Into the Vaginal Microbiome?

The vagina contains a dynamic community of microorganisms collectively known as the vaginal microbiome.

In many reproductive-aged women, Lactobacillus species are an important component of that ecosystem.

Species commonly encountered include:

• Lactobacillus crispatus

• Lactobacillus jensenii

• Lactobacillus gasseri

• Lactobacillus iners

Lactobacilli contribute to vaginal acidity, particularly through production of lactic acid, and Lactobacillus-dominant communities are commonly associated with vaginal health.

However, vaginal microbiomes are not identical between women and they can change over time.

Hormones, sexual activity, menstruation, pregnancy, medications, antimicrobial exposure and other biological and behavioural factors may influence the vaginal environment.

BV represents a substantial ecological shift away from the usual Lactobacillus-dominant pattern toward a more diverse community containing higher concentrations of anaerobic and other BV-associated bacteria.

Gardnerella is frequently prominent within that community.

But it rarely tells the entire story.

Does Gardnerella Mean You Have Bacterial Vaginosis?

No — not by itself.

This is probably the most important point in this article.

Gardnerella is strongly associated with BV, but its presence alone is not sufficiently specific to diagnose bacterial vaginosis.

In fact, culture of Gardnerella vaginalis alone is not recommended as a diagnostic test for BV because Gardnerella can also occur in people without the condition.

BV is traditionally diagnosed using established approaches such as Amsel clinical criteria or Nugent scoring of a vaginal Gram stain, while validated molecular tests can also assess patterns of BV-associated organisms in symptomatic women.

The important question therefore isn't simply:

“Do I have Gardnerella?”

It is:

“What does this Gardnerella result mean in the context of my symptoms and overall vaginal environment?”

What Is Bacterial Vaginosis?

Bacterial vaginosis is a polymicrobial vaginal dysbiosis.

Rather than being caused by one microorganism, BV is characterised by changes in the composition of the vaginal microbiota, typically involving reduced Lactobacillus dominance and increased abundance and diversity of BV-associated bacteria.

These may include:

• Gardnerella species

• Fannyhessea vaginae — previously known as Atopobium vaginae

• Prevotella species

• Mobiluncus species

• BV-associated bacteria such as BVAB2

• Megasphaera and other anaerobic organisms

The exact microbial pattern varies between women.

BV may cause:

• thin or increased vaginal discharge

• white or grey discharge

• a characteristic fishy vaginal odour

• odour that becomes more noticeable after sex

• vaginal discomfort in some women

But BV can also be asymptomatic.

This is another reason symptoms and individual organisms cannot be interpreted in isolation.

What Is Vaginal Dysbiosis?

Vaginal dysbiosis simply describes a disruption or alteration in the vaginal microbial community.

In BV, this typically involves a transition from a lower-diversity, Lactobacillus-dominant environment toward a more diverse community containing greater abundance of BV-associated organisms.

Gardnerella is commonly involved.

However:

Gardnerella ≠ dysbiosis ≠ automatically BV.

These concepts overlap, but they aren't interchangeable.

Someone can have detectable Gardnerella without having symptomatic BV.

Likewise, vaginal symptoms can occur for reasons completely unrelated to Gardnerella.

That distinction becomes particularly important with increasingly sensitive molecular testing, where detecting DNA from an organism does not necessarily establish that the organism is causing disease.

Detection does not equal disease.

Why Is Gardnerella Important in BV?

One of the most interesting aspects of Gardnerella biology is its association with biofilm formation.

A biofilm is an organised community of microorganisms attached to a surface and embedded within a protective extracellular matrix.

In BV, a dense polymicrobial biofilm can form along the vaginal epithelium.

Gardnerella is frequently a major component of this biofilm and has properties that allow it to adhere to vaginal epithelial cells. Other BV-associated organisms can subsequently become incorporated into the developing microbial community.

This has changed how researchers think about BV.

Rather than imagining free-floating Gardnerella bacteria causing a straightforward infection, we can think of BV in some women as involving an organised polymicrobial community attached to the vaginal surface.

Recent systematic research continues to support the polymicrobial nature of BV-associated biofilms.

Does Biofilm Explain Why BV Keeps Coming Back?

It may explain part of the recurrence problem, but it isn't the only explanation.

Biofilm-associated organisms can be more difficult to eradicate than bacteria living freely within vaginal fluid, and persistent or re-established biofilm has been investigated as one mechanism contributing to recurrent BV.

But recurrence is probably multifactorial.

Potential contributors include:

• persistence or re-emergence of BV-associated organisms

• failure to re-establish a stable Lactobacillus-dominant community

• sexual exchange of BV-associated bacteria

• exposure to an ongoing sexual partner

• hormonal changes

• menstruation

• individual microbiome characteristics

• other host and environmental factors

So I would be cautious about telling a woman:

“Your BV keeps coming back because you have a biofilm.”

Biofilm may be important, but recurrent BV deserves a broader assessment.

Why Does Gardnerella Keep Coming Back After Antibiotics?

This is another common question.

Recommended antimicrobial treatment can be very effective at treating an episode of BV and reducing BV-associated bacterial abundance.

But recurrence after apparently successful treatment is common.

That doesn't necessarily mean the antibiotic “failed.”

Treatment may substantially alter the vaginal microbial community, but what happens after treatment also matters.

Some women re-establish a more stable Lactobacillus-dominant microbiome. Others may transition back toward a BV-associated community.

Persistent biofilm, microbial community structure, sexual exposure and other biological factors may all contribute.

For this reason, recurrent BV is better understood as a problem involving microbial ecology and recurrence risk, rather than simply repeatedly acquiring one bacterium called Gardnerella.

Is Gardnerella an STI?

This question has become more nuanced.

Gardnerella itself should not simply be described as a conventional STI in the same way as chlamydia or gonorrhoea.

However, there is now substantial evidence that sexual activity and sexual partnerships play an important role in BV.

BV-associated bacteria can be shared between sexual partners, and BV has strong epidemiological associations with sexual exposure.

Current Australian STI Management Guidelines state that BV has the epidemiological profile of a sexually transmissible infection, including associations with new partners, increased numbers of sexual partners and lack of condom use for penile-vaginal sex.

This is an important shift from the older explanation that:

“BV isn't sexually transmitted.”

The current evidence is more complex than that.

Why Do I Keep Getting BV After Sex?

Many women notice a very clear pattern:

sex → vaginal change → odour/discharge → BV recurrence.

There may be several reasons.

Semen temporarily increases vaginal pH.

Sexual activity can also alter the vaginal environment mechanically and biologically.

Most importantly, research increasingly supports sexual exchange of BV-associated bacteria between partners.

BV-associated organisms have been identified on penile skin and within the male urethra, and bacterial communities can show concordance between sexual partners.

This helps explain why some women experience recurrent BV associated with an ongoing sexual partner.

Should Male Partners Be Treated for Recurrent BV?

This is one of the biggest recent changes in BV management.

Historically, male partner treatment was generally not recommended because older trials had not demonstrated sufficient benefit.

Then came the Australian StepUp trial.

The 2025 randomised controlled trial published in the New England Journal of Medicine compared treatment of women alone with simultaneous treatment of women and their ongoing male partners.

BV recurrence within 12 weeks occurred in:

35% of women in the partner-treatment group

compared with:

63% of women whose partners were not treated.

The trial was stopped early because treatment of the woman alone was inferior to concurrent partner treatment.

Australian STI Management Guidelines have subsequently incorporated concurrent partner treatment into BV management for people with an ongoing male partner.

This does not mean every Gardnerella result requires partner antibiotics.

Partner treatment relates to the management of diagnosed BV, not simply the detection of Gardnerella on a test.

That distinction is very important.

Can Hormones Influence BV and the Vaginal Microbiome?

Yes.

Oestrogen has important effects on vaginal tissue and the vaginal microbial environment.

Across reproductive life, hormonal changes can alter vaginal epithelial biology, glycogen availability, vaginal pH and microbial community composition.

This becomes particularly relevant during:

• perimenopause

• menopause

• postpartum changes

• breastfeeding

• other periods of substantial hormonal change

As oestrogen declines during menopause, Lactobacillus dominance often decreases and vaginal pH commonly increases.

This can substantially change the vaginal microbial environment.

However, symptoms during perimenopause or menopause should not automatically be attributed to Gardnerella or BV.

Genitourinary Syndrome of Menopause, vulvovaginal candidiasis, dermatological conditions, urinary disorders, sexually transmitted infections and other causes may produce overlapping symptoms.

What About Comprehensive Vaginal Microbiome Testing?

Comprehensive molecular vaginal microbiome testing can provide information beyond that available from some routine investigations.

Depending on the test used, this may include information about:

• Lactobacillus abundance

• Lactobacillus species

• Gardnerella species or abundance

• BV-associated anaerobes

• aerobic organisms

• Candida species

• selected sexually transmitted infections

• other microorganisms included within the particular panel

For women with persistent, recurrent or complex symptoms, this information may sometimes help provide a more detailed picture of the vaginal microbial community.

However, microbiome testing should not be interpreted as:

organism detected = organism causing symptoms = organism must be eradicated.

Molecular testing is extremely sensitive.

Clinical interpretation still matters.

For Gardnerella in particular, abundance, the broader microbial pattern, symptoms, previous treatment, vaginal pH where relevant and other investigations may all contribute to understanding what the result actually means.

When Is Gardnerella Actually Important?

Gardnerella becomes more clinically meaningful when it forms part of a broader pattern consistent with BV or significant vaginal dysbiosis.

For example, assessment may consider:

• vaginal odour or altered discharge

• recurrent BV episodes

• vaginal pH

• microscopy or Gram-stain findings where available

• abundance and diversity of BV-associated bacteria

• Lactobacillus composition

• treatment history

• recurrence after treatment

• relationship between symptoms and sexual activity

• hormonal stage

• other possible causes of symptoms

The goal is not to make one organism carry the entire diagnosis.

It is to understand the pattern.

What If Gardnerella Is Detected but I Have No Symptoms?

This is where unnecessary treatment can become a problem.

A Gardnerella result in an asymptomatic woman does not automatically mean that treatment is required.

Gardnerella can occur without BV, and the clinical significance of molecular findings depends on the testing method and clinical context.

If you receive an unexpected Gardnerella result, it is reasonable to ask:

What exactly was tested?

Why was the test performed?

Does the overall result indicate BV?

Do I actually have symptoms?

Is treatment clinically indicated?

Those questions are more useful than focusing on the word Gardnerella alone.

What If BV Keeps Returning?

If BV repeatedly returns despite treatment, simply repeating the same treatment indefinitely without reassessing the situation may not answer why recurrence is occurring.

A broader clinical review may consider:

• whether BV has been appropriately diagnosed

• whether another vaginal condition is contributing

• previous pathology and treatment response

• sexual recurrence patterns

• whether partner treatment is appropriate

• hormonal factors

• vaginal pH where relevant

• Lactobacillus and BV-associated microbial patterns

• whether additional investigations are indicated

The management plan will depend on the individual clinical picture.

When Should You See a GP or Sexual Health Clinician?

Telehealth can be useful for reviewing recurrent BV, previous pathology, treatment history, sexual patterns, hormonal factors and vaginal microbiome results.

However, not every vaginal symptom can or should be managed remotely.

You may need assessment by your GP, sexual health clinician, gynaecologist or another appropriate clinician when physical examination, microscopy, Gram staining, culture, STI testing or assessment of vulval or vaginal tissue is required.

Seek prompt medical assessment for significant pelvic or abdominal pain, fever or systemic illness, unexplained vaginal bleeding, new ulcers or genital lesions, rapidly worsening symptoms, or concerning symptoms during pregnancy.

A More Evidence-Informed Way to Think About Gardnerella

Gardnerella is neither:

“just normal flora and therefore irrelevant”

nor:

“a bad bacterium that must always be eradicated.”

Both explanations are too simplistic.

Gardnerella is a diverse genus strongly associated with bacterial vaginosis. Some Gardnerella species and strains appear to have characteristics that may make them more important in BV pathogenesis, including epithelial adhesion, biofilm formation and interactions with other BV-associated bacteria.

But Gardnerella can also be detected without BV.

The vaginal microbiome is an ecosystem, and the significance of Gardnerella depends on what is happening around it.

For women with recurrent BV, the most useful question therefore may not be:

“How do I get rid of Gardnerella?”

It may be:

“Why does my vaginal environment keep returning to a BV-associated state?”

That opens the door to a much more useful clinical discussion.

About Kylie Sayce NP

Kylie Sayce is an Australian Endorsed Nurse Practitioner with a clinical focus on recurrent vaginal and urinary conditions, vaginal microbiome health and women's sexual and reproductive health.

The Telehealth Clinic provides Australia-wide consultations for women experiencing recurrent BV, recurrent thrush, recurrent UTIs, aerobic vaginitis, persistent vaginal symptoms and vaginal microbiome disturbances.

For women with recurrent symptoms, consultations allow time to comprehensively review symptom patterns, previous pathology, treatment history, hormonal factors, vaginal pH where relevant and, where clinically appropriate, comprehensive vaginal microbiome testing.

My clinical approach is evidence-informed and focuses on understanding why symptoms are recurring rather than treating an isolated symptom or microbiome result in isolation.

Unsure what your Gardnerella result means — or why your BV keeps coming back?

If this sounds familiar, a dedicated women's health consultation can help review your history, previous results and recurrence pattern and determine what options may be worth considering.