Bacterial Vaginosis, Vaginal Microbiome, Women's Health

Biofilms and Recurrent BV: Why Bacterial Vaginosis Keeps Coming Back

“I’ve taken the antibiotics. The symptoms improved. Then a few weeks later, the odour and discharge came back.”

For women living with recurrent bacterial vaginosis (BV), this cycle can be incredibly frustrating.

Treatment may work very well initially — and yet the vaginal environment can shift back toward BV again.

Why?

There is unlikely to be one explanation for every woman. Recurrent BV can involve several overlapping factors, including:

• persistence or re-emergence of BV-associated bacteria

• polymicrobial biofilm

• difficulty re-establishing a stable Lactobacillus-dominant vaginal environment

• sexual exchange of BV-associated bacteria

• menstrual and pH-related changes

• hormonal factors

• antimicrobial exposure

• individual vaginal microbiome characteristics

One of the most important developments in BV research has been the recognition that BV-associated organisms can form structured polymicrobial biofilms attached to the vaginal epithelium. [1,2]

That helps explain why recurrent BV is not simply:

“one bacterium that needs to be killed.”

But there is an equally important caution.

We do not currently have a clinically proven method for simply “stripping away” or permanently eradicating BV biofilm.

A 2024 systematic review identified 35 studies investigating potential BV antibiofilm agents, but 89% were preclinical laboratory studies, and most examined experimental agents rather than established clinical treatments. [3]

That is why I approach recurrent BV using both established treatment and an evidence-informed, integrative framework that considers the vaginal ecosystem as a whole.

What Is Bacterial Vaginosis?

Bacterial vaginosis is a polymicrobial vaginal dysbiosis.

In many reproductive-aged women, the vaginal microbiome is dominated by Lactobacillus species.

These organisms help maintain an acidic vaginal environment through lactic-acid production and are commonly associated with vaginal health.

In BV, the vaginal microbial community shifts toward greater diversity and higher abundance of anaerobic BV-associated bacteria.

These may include:

• Gardnerella species

• Fannyhessea vaginae

• Prevotella species

• Mobiluncus species

• Megasphaera

• BV-associated bacteria such as BVAB2

• other anaerobic organisms

Current Australian STI Management Guidelines describe BV as a polymicrobial vaginal dysbiosis and recognise an adherent polymicrobial biofilm on vaginal epithelial cells as part of BV biology. [5]

What Is a Vaginal Biofilm?

A biofilm is an organised community of microorganisms that attaches to a surface and becomes embedded within an extracellular matrix.

Biofilms occur throughout nature and the human body.

Dental plaque is one familiar example.

In BV, researchers have demonstrated dense bacterial communities attached directly to vaginal epithelial cells using microscopy and fluorescence in-situ hybridisation. [1]

This means BV-associated organisms are not necessarily just free-floating within vaginal fluid.

They may live together in a structured microbial community along the vaginal surface.

Within a biofilm, bacteria can behave differently from free-floating organisms, including changes in metabolism, gene expression and antimicrobial tolerance. [3]

Where Does the BV Biofilm Actually Live?

BV-associated biofilm develops along the vaginal epithelium — the cells lining the vaginal surface. [1]

Swidsinski and colleagues demonstrated dense bacterial biofilms adherent to vaginal epithelial tissue, with Gardnerella forming a major component of these communities. [1]

The classic BV clue cell is essentially a vaginal epithelial cell coated with bacteria.

This matters because biofilm is not simply:

“a layer that can be washed away.”

Douching or aggressive vaginal cleansing does not remove the underlying microbial ecology and can further disturb the vaginal environment.

What Role Does Gardnerella Play in BV Biofilm?

Gardnerella is strongly associated with BV and frequently forms a major structural component of BV-associated biofilm.

Research suggests Gardnerella can:

• adhere strongly to vaginal epithelial cells

• initiate or support biofilm development

• interact with other BV-associated bacteria

• contribute to extracellular matrix formation

• create conditions that allow other anaerobic organisms to become established [1–3]

Once this microbial community develops, organisms such as Fannyhessea vaginae and Prevotella may become incorporated into the biofilm.

This is why BV is better understood as a polymicrobial ecological disturbance rather than simply a Gardnerella infection.

What Did the Swidsinski Biofilm Studies Show?

Some of the most important clinical evidence came from Alexander Swidsinski and colleagues.

In an early study, vaginal biopsy specimens from women with BV demonstrated adherent polymicrobial bacterial biofilms on the vaginal epithelium, with Gardnerella making up a major proportion of the bacterial mass. [1]

A subsequent study followed women treated with standard oral metronidazole.

Although the women initially recovered clinically, researchers observed resurgence of dense and metabolically active biofilm after treatment stopped, predominantly involving Gardnerella and Atopobium vaginae — now known as Fannyhessea vaginae. [4]

This demonstrated an important concept:

Clinical improvement does not necessarily mean every BV-associated bacterial reservoir has been eliminated.

However, these studies do not prove that antibiotics are incapable of reaching biofilm.

Metronidazole clearly remains an effective treatment for many women with symptomatic BV.

The more accurate interpretation is that biofilm-associated bacterial communities may persist or re-emerge after treatment in some women, potentially contributing to recurrence. [4]

Can BV Biofilm Make Antibiotics Less Effective?

Biofilm-associated organisms may be more tolerant of antimicrobial exposure than free-floating bacteria.

Within the biofilm environment, bacteria may show:

• altered metabolism

• reduced growth rates

• different gene expression

• increased tolerance to antimicrobials

• cooperative interactions between species [3]

That may contribute to persistence.

But antibiotics remain standard-of-care treatment for symptomatic BV.

Australian guidance recommends metronidazole or clindamycin regimens as first-line therapy. [5]

So I would not describe the problem as:

“antibiotics cannot penetrate the biofilm.”

A more accurate interpretation is:

Antibiotics can successfully treat the acute BV episode while the broader vaginal ecosystem may remain vulnerable to recurrence.

Why Does BV Keep Coming Back After Treatment?

Recurrence probably occurs through several different pathways.

Persistence of BV-associated organisms

Some organisms may survive at low abundance and subsequently expand again.

Biofilm persistence or reformation

A BV-associated microbial structure may persist or re-form. [4]

Failure to establish a stable Lactobacillus-dominant environment

Some women rapidly regain Lactobacillus dominance after treatment, while others do not.

Sexual reinfection

BV-associated organisms can be exchanged between partners, and current Australian evidence now strongly supports sexual reinfection as an important contributor to recurrent BV. [5,9]

Menstruation and vaginal pH

Menstrual blood can temporarily raise vaginal pH and influence the vaginal microbial environment.

Hormonal factors

Perimenopause, menopause and other hormonal states can alter the vaginal epithelium, pH and microbial composition.

Individual microbial communities

Different women begin with different vaginal ecosystems and may respond differently to antimicrobial treatment.

This is why recurrent BV should not be reduced to one explanation.

What Do We Know About Gardnerella and Recurrence?

Older and newer molecular studies support the idea that recurrence relates to microbial community composition, rather than merely Gardnerella being present or absent.

Bradshaw and colleagues found that women with both Gardnerella vaginalis and Atopobium vaginae had a substantially higher recurrence rate after oral metronidazole than women in whom Gardnerella was detected alone — 83% versus 38% in that study. [11]

More recent longitudinal work has also found associations between specific Gardnerella groups, other BV-associated bacteria, Lactobacillus recovery and whether women experience remission, recurrence or refractory disease after metronidazole. [12,13]

The important message is:

BV recurrence is about the microbial community, not simply whether Gardnerella is detected.

What About Boric Acid?

Boric acid is where the biofilm discussion becomes particularly interesting.

Vaginal boric acid has been used in selected recurrent vulvovaginal conditions for many years and has increasingly been incorporated into recurrent-BV regimens.

It is frequently described online as a “biofilm disruptor.”

There is biological plausibility behind that term, but the clinical evidence needs to be interpreted carefully.

Boric acid may influence:

• vaginal acidity

• microbial growth

• microbial adhesion

• extracellular biofilm structures

However, we do not currently have a high-quality human trial demonstrating that standard vaginal boric acid capsules physically eradicate Gardnerella biofilm from the vaginal epithelium.

What Was the Reichman Boric Acid Regimen?

A frequently cited 2009 study by Reichman, Akins and Sobel evaluated a three-stage recurrent-BV regimen. [6]

Importantly, this was not a randomised controlled trial.

It was an uncontrolled retrospective chart review.

Women received:

• oral nitroimidazole for 7 days

• followed by 600 mg intravaginal boric acid daily for 21 days

• followed by twice-weekly vaginal metronidazole gel for 16 weeks if remission had been achieved

After the nitroimidazole and boric acid phase, reported cure rates were approximately:

88% at 7 weeks

and

92% at 12 weeks. [6]

Cumulative cure declined with longer follow-up to approximately 65% at 28 weeks, and a 50% failure rate was documented by 36 weeks. [6]

This study was important because it established a clinical framework combining:

antimicrobial induction → boric acid → suppression.

But because there was no comparator group, the study cannot establish that boric acid itself produced the outcome or prove that it physically removed biofilm.

What Did the 2021 Combination-Therapy Study Show?

Surapaneni, Akins and Sobel later reported experience with 105 women with recurrent BV who had failed recommended regimens. [7]

Their regimen involved:

• oral nitroimidazole twice daily for 7 days

• simultaneous vaginal boric acid 600 mg daily for 30 days

• followed by twice-weekly vaginal metronidazole gel for five months

Among the women available for early assessment, 92 of 93 achieved an initial satisfactory response. [7]

Among compliant participants, suppressive metronidazole prevented symptomatic recurrence in approximately 69.6% at six months, and long-term cure was observed in approximately 69% of women reaching the later observation phase. [7]

However, the study was an uncontrolled retrospective cohort, so it does not establish the independent effect of boric acid.

It also identified an important clinical consequence:

Vulvovaginal candidiasis frequently complicated prolonged antimicrobial suppression. [7]

That matters when considering long-term strategies.

What Does the Newer 2025 Boric Acid Study Add?

A 2025 retrospective observational study examined 52 women with recurrent BV who had failed or rapidly recurred following metronidazole or clindamycin. [8]

Participants received:

600 mg intravaginal boric acid daily for 14 days.

At Day 30:

• mean Nugent score fell from 7.8 to 3.1

• 88.5% achieved a Nugent score below 4

• clue cells were markedly reduced

• vaginal odour improved

• vaginal-health and patient-reported outcomes improved [8]

These are encouraging short-term findings.

But the limitations are important.

The study was:

• retrospective

• single-arm

• relatively small

• limited to short-term follow-up

It therefore cannot determine whether boric acid is superior to standard therapy or whether the improvements persist long term. [8]

Importantly:

The study did not directly measure or demonstrate biofilm eradication.

Does Boric Acid Actually Break Down Gardnerella Biofilm?

This is the key distinction.

Laboratory and mechanistic evidence provides reasons to believe boric acid may have effects relevant to biofilm.

Clinical recurrent-BV regimens containing boric acid have also produced encouraging outcomes. [6–8]

But there is currently no high-quality human clinical trial demonstrating that standard vaginal boric acid directly strips Gardnerella biofilm from the vaginal epithelium.

A 2024 systematic review of antibiofilm agents found that most research in this area remains laboratory-based. [3]

So my evidence-informed interpretation is:

Boric acid may be a useful adjunct in selected recurrent or refractory BV and may exert actions relevant to biofilm biology, but it should not be described as a proven biofilm “eraser”.

What About TOL-463?

TOL-463 is an investigational vaginal formulation containing boric acid and EDTA that has been studied because of its potential antimicrobial and antibiofilm properties.

A phase 2 study reported BV clinical cure rates of approximately:

59% with the vaginal insert

and

50% with the vaginal gel. [14]

The formulation was generally well tolerated.

However, this did not establish that TOL-463 was superior to standard BV treatment or directly demonstrate clinical biofilm eradication.

It is therefore useful as evidence that biofilm-targeted vaginal treatment is an active area of research, rather than proof that boric acid alone eliminates BV biofilm.

What Do Systematic Reviews Say About Antibiofilm Treatments?

The 2024 review by Gao and colleagues examined 35 studies investigating potential agents for BV biofilm treatment or prevention. [3]

Potential strategies included:

• antibiotics

• antiseptics

• enzymes

• antimicrobial peptides

• plant-derived compounds

• probiotics

• surfactants

• other experimental agents

However, 89% of the included studies were preclinical, meaning the evidence came largely from laboratory rather than human clinical research. [3]

That is a very important distinction.

There is substantial scientific interest in biofilm disruption.

But:

A promising effect in a laboratory model is not the same thing as proven clinical eradication of vaginal BV biofilm.

Where Does Lactobacillus Fit In?

Treating BV-associated organisms is only one part of the ecological picture.

Another important question is:

What replaces them after treatment?

Lactobacillus crispatus has become particularly important in this research.

The randomised, double-blind LACTIN-V trial studied a specific vaginal Lactobacillus crispatus CTV-05 live biotherapeutic after women had completed vaginal metronidazole treatment. [10]

BV recurrence by 12 weeks occurred in:

30% of women receiving LACTIN-V

compared with

45% receiving placebo. [10]

The relative risk of recurrence was approximately 0.66.

This provides important clinical evidence that post-treatment establishment of specific Lactobacillus strains may influence recurrence.

But it is essential not to overgeneralise.

LACTIN-V is:

• a specific strain

• a specific formulation

• a controlled investigational live biotherapeutic

The results should not automatically be applied to every commercial Lactobacillus probiotic.

Can Probiotics Help Prevent Recurrent BV?

The evidence continues to evolve.

A 2026 network meta-analysis of randomised controlled trials found that:

• partner treatment reduced recurrence

• vaginal probiotics reduced early recurrence/persistence

• oral probiotics also showed benefit in some analyses

• vaginal probiotics were the only intervention reaching statistical significance overall in long-term prevention

• acidifying strategies also showed benefit in some settings [15]

The certainty varied by intervention and population. [15]

This newer evidence is important because it suggests microbiome-directed strategies deserve continued consideration.

However, this evidence still does not mean:

all probiotics work

or

every woman with recurrent BV should take probiotics.

Species, strain, route, dose and timing matter.

Can Sex Re-Establish BV-Associated Bacteria?

Yes.

This is now one of the strongest emerging explanations for some recurrent BV.

BV-associated organisms can be exchanged between sexual partners.

Current Australian STI guidance recognises reinfection from an ongoing sexual partner as an important contributor to BV recurrence. [5]

This means recurrence after sex may involve more than a temporary rise in vaginal pH from semen.

It may also involve reintroduction or exchange of BV-associated microbial communities.

What Did the StepUp Partner-Treatment Trial Show?

The Australian StepUp trial fundamentally changed the discussion around recurrent BV. [9]

This open-label randomised controlled trial compared:

woman-only BV treatment

with

simultaneous treatment of the woman and her ongoing male partner.

BV recurrence within 12 weeks occurred in:

35% of women whose partners were also treated

versus

63% of women receiving woman-only treatment. [9]

The trial was stopped early because woman-only treatment was inferior to concurrent partner treatment. [9]

These findings have now been incorporated into Australian STI Management Guidelines. [5]

Should an Ongoing Male Partner Be Treated?

Current Australian guidance recommends concurrent treatment of an ongoing or regular partner with a penis when treating vaginal BV. [5]

This is a major change from historical practice.

Partner treatment does not mean someone is “dirty” or that BV behaves exactly like chlamydia or gonorrhoea.

It reflects growing evidence that BV-associated microbial communities can be exchanged between partners. [5,9]

What About Partners With Vaginas?

Evidence is less developed.

BV concordance is high between partners with vaginas, but comparable partner-treatment randomised trials are not yet available.

Current Australian guidance recommends assessment/testing of an ongoing partner with a vagina and treatment if BV is diagnosed. [5]

What About Vaginal pH?

Vaginal pH is another part of the ecological picture.

Lactobacillus-dominant vaginal communities generally maintain an acidic vaginal environment.

BV commonly occurs with a vaginal pH above 4.5. [5]

However, vaginal pH is not diagnostic by itself.

It can also be influenced by:

• semen

• menstruation

• hormonal changes

• lower-oestrogen states

So simply trying to “acidify the vagina” does not automatically resolve the underlying microbial community.

The Integrative Question: What Happens After the Antibiotic?

This is where recurrent BV becomes more than an acute infection-management problem.

Conventional treatment answers:

“How do we treat the active BV?”

But recurrent BV also raises other questions:

• What happened to the Lactobacillus community afterwards?

• Is an ongoing sexual partner contributing to reinfection?

• Is vaginal pH repeatedly being destabilised?

• Do symptoms cluster around menstruation?

• Are hormonal changes affecting vaginal tissue or microbial stability?

• Has repeated antimicrobial exposure changed the ecosystem?

• Could Candida now be contributing?

• Is the diagnosis actually BV each time?

• Are aerobic organisms or another form of vaginitis relevant?

• Would comprehensive vaginal microbiome testing provide useful additional information?

These questions do not replace established medical treatment.

They sit alongside it.

That is what I mean by an integrative, evidence-informed approach.

My Clinical Framework for Recurrent BV

For complex recurrent cases, I organise management using:

RESET → REBUILD → RESTORE → MAINTAIN → RESCUE

This is my clinical framework, rather than a formally validated BV guideline.

The individual interventions vary according to diagnosis, pregnancy status, pathology, previous treatment response, recurrence pattern, sexual circumstances, hormonal factors and individual risk.

RESET — Treat the Active BV

RESET begins by identifying and treating the active condition.

This may include:

• confirming that BV is actually present

• reviewing previous pathology

• STI testing where appropriate

• evidence-based antimicrobial treatment [5]

• concurrent partner treatment where appropriate [5,9]

• consideration of recurrent-BV strategies in selected patients

• consideration of adjunctive approaches such as boric acid where clinically appropriate and after individual assessment [6–8]

The purpose is not to sterilise the vagina.

It is to reduce the clinically relevant BV-associated burden.

REBUILD — Consider the Post-Treatment Microbial Environment

After active BV has been treated, the next question is:

What microbial community is emerging?

Depending on the patient, I may consider:

• Lactobacillus abundance

• Lactobacillus species

• treatment response

• vaginal pH

• recent antimicrobial exposure

• symptoms suggesting another condition

The L. crispatus evidence makes this phase particularly interesting. [10]

But I distinguish between specific Lactobacillus strains that have clinical trial evidence and generic probiotic products.

RESTORE — Address Factors Affecting Vaginal Stability

RESTORE considers factors that may influence the vaginal environment over time.

This may include:

• sexual recurrence patterns

• partner treatment [5,9]

• menstruation

• vaginal pH

• hormonal status

• perimenopause or GSM

• unnecessary antimicrobial exposure

• irritating vaginal products

• microbiome-directed strategies where evidence and individual circumstances support them

The objective is not to force every woman into a theoretical “perfect microbiome.”

The goal is a stable, symptom-free vaginal environment.

MAINTAIN — Reduce Future Recurrence

Some women require a longer-term recurrence-prevention strategy.

Evidence-based approaches can include suppressive antimicrobial therapy in selected patients. [5]

Newer evidence also supports continued research and consideration of partner treatment, probiotics and acidifying approaches in appropriate contexts. [9,15]

The maintenance strategy should be individualised.

RESCUE — Have a Plan for the Next Flare

Women with recurrent BV often know their symptom patterns.

Recurrence may follow:

• sex

• menstruation

• antibiotics

• hormonal transitions

• long symptom-free periods

A RESCUE strategy means knowing when to:

• repeat testing

• confirm BV

• assess for STIs

• consider Candida

• consider aerobic vaginitis or another vaginal condition

• review partner factors

• seek face-to-face assessment

Not every recurrent episode should automatically be assumed to be BV.

Where Do Diet and Lifestyle Fit?

I use integrative concepts carefully.

General vaginal and metabolic health may be supported by:

• avoiding vaginal douching

• avoiding fragranced intravaginal products

• reducing unnecessary antimicrobial exposure

• smoking cessation

• adequate fibre

• a diverse plant-rich diet

• adequate protein and micronutrient intake

• supporting overall gastrointestinal health

• addressing hormonal factors where relevant

But there is currently no high-quality evidence that a particular diet removes Gardnerella biofilm or cures recurrent BV.

Likewise, supplements marketed as “biofilm breakers” should not automatically be assumed to remove vaginal biofilm simply because they demonstrate laboratory antimicrobial activity.

What About Comprehensive Vaginal Microbiome Testing?

Routine uncomplicated BV does not require comprehensive vaginal microbiome mapping.

In selected women with persistent, recurrent or complex symptoms, molecular vaginal microbiome testing may provide additional information about:

• Lactobacillus abundance

• Lactobacillus species

• Gardnerella

• Fannyhessea vaginae

• other BV-associated organisms

• aerobic bacteria

• Candida species

• selected STIs

• other microorganisms included within the panel

This can help characterise the broader microbial environment.

However:

Molecular microbiome testing cannot tell us whether a physical biofilm is present.

And:

Detection does not equal disease.

Results still need to be interpreted alongside symptoms, clinical history, previous pathology, pH, treatment history and appropriate conventional testing.

When Should Recurrent BV Be Reassessed?

If symptoms continue to return, it is worth confirming that BV is actually responsible.

Other causes can include:

• vulvovaginal candidiasis

• aerobic vaginitis

• trichomoniasis

• sexually transmitted infections

• Genitourinary Syndrome of Menopause

• desquamative inflammatory vaginitis

• vulval dermatological conditions

• irritant or allergic conditions

• other causes of vaginal discharge or odour

Persistent symptoms deserve reassessment rather than indefinite empirical treatment.

When Should You See a GP or Sexual Health Clinician?

Telehealth can be useful for reviewing recurrent BV, previous pathology, treatment response, partner factors, vaginal pH, hormonal influences and vaginal microbiome results.

However, some presentations require face-to-face assessment.

A GP, sexual health clinician, gynaecologist or another appropriate clinician may be needed for:

• pelvic or vulvovaginal examination

• microscopy or Gram staining

• specimen collection

• STI assessment

• persistent unexplained symptoms

• abnormal vaginal bleeding

• pelvic pain

• vulval lesions, ulceration or skin changes

Seek prompt assessment for severe pelvic or abdominal pain, fever or systemic illness, significant unexplained bleeding, rapidly worsening symptoms or concerning symptoms during pregnancy.

The Bigger Picture: Biofilm Matters — But It Is Not the Whole Story

Biofilm has substantially changed our understanding of bacterial vaginosis.

It provides strong evidence that BV-associated bacteria can live within organised polymicrobial communities attached to vaginal epithelial cells. [1–4]

Clinical recurrent-BV studies also suggest potential value from strategies that go beyond another isolated short course of antibiotics — including partner treatment, suppressive therapy, selected boric-acid-containing regimens and microbiome-directed approaches. [6–10,15]

But we should not replace one oversimplification:

“BV is just Gardnerella.”

with another:

“BV is just a biofilm.”

The evidence points toward a much more complex ecological model:

BV-associated bacteria + biofilm + Lactobacillus recovery + sexual reinfection + vaginal pH + hormones + individual host factors.

That is why my approach combines established medical treatment with a broader evidence-informed and integrative assessment of why the vaginal environment keeps returning to a BV-associated state.

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 recurrent BV, consultations allow time to comprehensively review previous pathology, antimicrobial treatment, recurrence patterns, sexual and partner factors, hormonal influences, vaginal pH and, where clinically appropriate, comprehensive vaginal microbiome testing.

My clinical approach is evidence-informed and integrative, combining established medical management with careful consideration of vaginal microbial ecology and emerging microbiome science.

Is Your BV Still Coming Back?

If you have had repeated BV treatment but symptoms continue to return, a comprehensive review can help determine whether BV is recurring, identify possible contributing factors and consider which evidence-informed management options may be appropriate.