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If your bacterial vaginosis keeps coming back no matter how many rounds of treatment you do, the bacterial biofilm is usually the reason. A biofilm is a sticky, living shield that disruptive bacteria – mostly Gardnerella – build over your vaginal cells. It hides the colony from your treatments and from your own protective bacteria, so antibiotics knock back the surface but leave the hidden bacteria sitting underneath, ready to regrow. That is why up to 80 per cent of women have BV back within a year of finishing antibiotics.1 Once you understand the biofilm, though, you can treat it properly instead of going round in circles.
What is a bacterial biofilm?
Bacterial biofilms occur all throughout nature. They are a great strategy for bacteria to form a strong colony without having to be everywhere at once, and without being washed away or killed easily.
A biofilm is a community of bacteria stuck to a surface and wrapped in a self-made matrix of proteins, sugars and DNA. It is a bit like a gated suburb the bacteria build for themselves, with the matrix doing the wall-and-moat job.
The biofilm jellanalogy
Imagine a jelly/jello cup with small pieces of fruit in it – raspberries, blueberries. The jelly/jello (the dessert, not jam you put on bread!) is the biofilm, while the fruit scattered within it is the bacteria, yeast and viruses that hide in biofilms.
If you pour liquid cream on the top of the jelly/jello, it doesn’t penetrate but sits on top. This is what your treatments are doing – sitting on top of the biofilm, not getting to the bacteria where they are required. That’s one reason that treatments repeatedly fail. Biofilms also create a barrier to other microbes.
Recurrent bacterial vaginosis (BV), vaginal dysbiosis, urinary tract infections (UTIs) and yeast infections can all become stubborn when one or more bacteria have made a biofilm on the vaginal cells, creating a layer that most treatments, including antibiotics, struggle to get through.2
Treatments kill the planktonic, free-floating bacteria, but do not touch the colony of bacteria hidden underneath the biofilm.
Why biofilms exist
A bacterial biofilm may occur in a wound, preventing healing, and can grow around medical implants and catheters, forming thick layers that stick closely to surfaces. Dental plaque is a biofilm, which is why it can get scraped off – and always grows back (the bacteria in your mouth don’t change that much).
The biofilm is a living shield of bacteria and protein matrix stuck to the vaginal walls, keeping other bacteria as easily-managed planktonic bacteria – protective or disruptive, it doesn’t matter. Protective species also make biofilms, so biofilms aren’t bad in and of themselves. They also keep protective colonies in place.
All bacteria work by producing substances that are destructive to other competitive bacteria (bacteriocins, biofilms) and by binding to the vaginal cells, providing a physical barrier to competitors. Biofilms are one such tool.
Why does BV keep coming back?
This is the part nobody warns you about when they hand you a script. In one well-known study that followed women for a year after standard metronidazole, more than half had a recurrence, and by 12 months the recurrence rate climbed to around 80 per cent.1 If you have felt like BV is a revolving door, you are not imagining it, and you are very much not alone.
The biofilm is a big reason why. When researchers looked at vaginal cells from women with BV under fluorescence microscopy, they found a dense, adherent biofilm dominated by Gardnerella stuck firmly to the vaginal wall – and that biofilm was still sitting there after antibiotic treatment, even when symptoms had settled.3 The treatment clears the free-floating bacteria and calms the smell and discharge, but the fortress underneath survives and slowly repopulates.
So recurrence usually isn’t because you did something wrong, or weren’t clean enough (BV has nothing to do with being unclean). It’s the biofilm surviving the treatment and quietly rebuilding, the way biofilms are built to.
Which bacteria build the BV biofilm?
Gardnerella is the main builder. It’s the keystone species that lays down the initial scaffold on the vaginal cells, and then other disruptive bacteria – such as Prevotella, Fannyhessea vaginae (formerly Atopobium vaginae) and others – move in and join the structure.2 The result is a mixed, polymicrobial biofilm rather than a single-species one, which is part of why it’s so hard to shift.
Plenty of older articles get this wrong: Gardnerella is no longer thought of as a single type of bacteria. In 2019, whole-genome sequencing split the genus into several distinct species, including Gardnerella vaginalis, Gardnerella leopoldii, Gardnerella piotii and Gardnerella swidsinskii, with more genomic groups behind them.4 These species differ in how aggressively they build biofilms and produce virulence factors, which may help explain why BV behaves so differently from one woman to the next, and why a one-size-fits-all approach so often misses.
If you want to know what is actually living in your vagina rather than guessing, this is where a comprehensive vaginal microbiome test earns its keep – it can show you the specific organisms and rough proportions, which makes targeted treatment possible. A standard swab or Amsel’s clinical diagnosis tells you that you have BV, but not the full cast of characters. The same goes for understanding clue cells and the BVAB markers some tests report.
Why don’t antibiotics work on the biofilm?
The bacterial biofilm is by its very nature resistant – but not completely immune – to the hydrogen peroxide and lactic acid produced by your protective vaginal lactobacilli.2 If the vagina is dysbiotic (the wrong bacteria in the wrong place), such as in BV, aerobic vaginitis (AV), yeast infections and UTIs, protective lactobacilli can be shut out.
Frustratingly, biofilms are also resistant to even high doses of antibiotics. The matrix physically slows the drug down, and the bacteria deep inside go into a slow, dormant state where antibiotics, which mostly target actively dividing bacteria, barely touch them.5 The matrix is rich in proteins and DNA, and that dense scaffolding is a large part of what shields the bacteria from being broken down.5
So antibiotics do not degrade the biofilm; they simply put a couple of bullet holes in it. When you stop taking them, the problem returns as if nothing happened. The biofilm is a protective living cocoon, an ingenious evolutionary survival trick – which is exactly why so many over-the-counter and prescription options that work on the surface keep letting you down. (We go through the realistic options in our guide to over-the-counter BV treatments.)
How the biofilm affects your vagina
A biofilm doesn’t just make BV stubborn – it changes the whole environment of your vagina. By holding disruptive bacteria firmly against the vaginal wall and crowding out protective lactobacilli, it keeps your vaginal pH higher than it should be, which makes it even harder for the protective bacteria to re-establish.2 It becomes a self-reinforcing loop: the wrong bacteria hold the territory, the pH stays unfriendly to the right ones, and the biofilm protects the whole arrangement.
That’s also why biofilm-driven dysbiosis often shows up as more than one problem. The same disrupted, lactobacilli-poor environment that allows BV to take hold can leave you more prone to recurrent UTIs and yeast infections, and the symptoms – discharge, odour, irritation – tend to return in cycles rather than clearing for good. If you treat the surface infection but never address the biofilm and the pH, it keeps finding its way back.
Here at My Vagina, we see people with treatment-resistant BV all the time, and biofilms can play a major part in why antibiotics don’t work very well. While it’s often not the only issue, ensuring treatments address biofilms while working on the other factors involved in BV can mean optimising treatments and more successful outcomes.
Can you actually break down a BV biofilm?
This is where the research is moving fast. Tackling the biofilm as part of treatment – rather than just hitting the free-floating bacteria – is increasingly seen as the missing piece for long-term success, and several approaches are being studied.5 None of this is a magic bullet you can buy off a shelf, and the strongest results come from combining strategies, ideally with a practitioner guiding the plan.
Agents that loosen the matrix
In laboratory studies, boric acid and the chelating agent EDTA have both shown a real ability to disrupt established BV biofilms and to make the bacteria inside more vulnerable to other treatments.5 A boric-acid-based product, TOL-463, reached around 50–59 per cent early clinical cure in a small randomised trial, and an anti-biofilm vaginal gel (astodrimer) has also been studied for BV.5 We dig into the detail – and the limits of the evidence – in our article on whether boric acid can really disrupt BV biofilms. Boric acid is for vaginal use only, never taken by mouth, and is not used in pregnancy.
Enzymes that dissolve the scaffold
Because the matrix is so protein- and DNA-rich, researchers are testing enzymes that chew through it – including DNase and dispersin B – to crack the biofilm open so antibiotics can finally reach the bacteria inside.5 This is still early-stage and mostly experimental, but it’s a promising direction, and natural agents with matrix-loosening potential (like the compounds explored in our piece on aloe vera and biofilms) sit in the same broad camp.
Rebuilding the protective colony
Clearing the biofilm is only half the job – you also have to get protective bacteria back in to hold the territory and keep the pH low. In a randomised trial, a live Lactobacillus crispatus vaginal probiotic (Lactin-V) given after antibiotics significantly reduced BV recurrence compared with placebo, which fits the idea that re-seeding the right bacteria matters.6 Restoring vaginal pH with lactic acid is part of the same logic. (Full vaginal microbiome transplants are being explored too, though as we explain, they aren’t reliably working yet.)
Don’t forget your partner
One of the biggest recent shifts in thinking is about reinfection. Recurrence is strongly linked to sexual factors – an ongoing sexual partner, not using condoms and having an uncircumcised partner all raise the odds of BV coming back – which is a large part of why attention has turned to treating partners rather than the woman alone.7
A 2025 randomised trial found that when male partners were treated at the same time as the woman (oral plus topical antimicrobials), BV recurrence at 12 weeks dropped to 35 per cent, compared with 63 per cent when only the woman was treated.8
The biofilm can persist on partners, so if it keeps boomeranging back, treating the woman alone may simply not be enough. This is an emerging area, but it’s an important one for anyone stuck in the recurrence cycle.
What this means for you
If you’ve done round after round of treatment and BV keeps coming back, the biofilm is almost certainly part of your story – and that’s good to know, because it points to what actually works: addressing the biofilm, restoring your protective bacteria and pH, and looking at reinfection, rather than just repeating the same short course and hoping.
- Get a clear picture first. A comprehensive vaginal microbiome test shows what’s actually there, so treatment can be targeted rather than guessed.
- Think in terms of a plan, not a single product. Loosening the biofilm, clearing the bacteria, and rebuilding protective lactobacilli are three different jobs.
- Use the free guides. Our Killing BV treatment guides walk through a structured, biofilm-aware approach step by step.
- Get tailored help if you’re stuck. You can book an appointment to work through your specific situation.
A quick note on scope: we’re a naturopathic vulvovaginal clinic and we don’t do internal or speculum examinations ourselves. If you need a physical exam or have red-flag symptoms – fever, pelvic pain, unusual bleeding, or anything that feels acutely wrong – see your doctor or a sexual-health clinic alongside any microbiome work.
Frequently asked questions
What is a biofilm in bacterial vaginosis?
It’s a sticky layer of disruptive bacteria – mainly Gardnerella – wrapped in a self-made matrix and glued to your vaginal cells. It shelters the bacteria from antibiotics and from your own protective lactobacilli, which is why BV becomes so hard to clear for good.2
Why does my BV keep coming back after antibiotics?
Antibiotics clear the free-floating bacteria and settle symptoms, but they leave the biofilm itself largely intact on the vaginal wall, so the colony quietly regrows. Studies show recurrence rates of up to 80 per cent within a year of standard treatment.3,1
Does boric acid break down the biofilm?
Boric acid shows real biofilm-disrupting activity in laboratory studies and has modest clinical evidence, especially alongside antibiotics, but it’s not a stand-alone cure.5 It’s for vaginal use only, never swallowed, and not used in pregnancy.
Is BV contagious or sexually transmitted?
BV isn’t classed as a classic STI, but sex clearly influences it, and recent evidence shows treating male partners alongside the woman lowers recurrence – suggesting the biofilm and its bacteria can be passed back and forth.8
Can probiotics help with a BV biofilm?
Re-seeding protective bacteria is an important part of stopping recurrence. A vaginal Lactobacillus crispatus probiotic used after antibiotics reduced recurrence in a randomised trial, though the right strain and timing matter.6
How do I know if I have a biofilm?
There’s no simple at-home test for the biofilm itself, but persistent or rapidly recurrent BV that returns after each round of treatment is the practical clue. A comprehensive microbiome test can show the disruptive bacteria involved and help shape a targeted plan.
This article is general information, not a substitute for personalised medical advice. If your symptoms are severe, persistent, or worrying, please see a qualified health practitioner.
- Bradshaw CS, Morton AN, Hocking J, et al. High recurrence rates of bacterial vaginosis over the course of 12 months after oral metronidazole therapy and factors associated with recurrence. The Journal of Infectious Diseases. 2006;193(11):1478–1486.
- Verstraelen H, Swidsinski A. The biofilm in bacterial vaginosis: implications for epidemiology, diagnosis and treatment: 2018 update. Current Opinion in Infectious Diseases. 2019;32(1):38–42.
- Swidsinski A, Mendling W, Loening-Baucke V, et al. Adherent biofilms in bacterial vaginosis. Obstetrics & Gynecology. 2005;106(5 Pt 1):1013–1023.
- Vaneechoutte M, Guschin A, Van Simaey L, Gansemans Y, Van Nieuwerburgh F, Cools P. Emended description of Gardnerella vaginalis and description of Gardnerella leopoldii sp. nov., Gardnerella piotii sp. nov. and Gardnerella swidsinskii sp. nov., with delineation of 13 genomic species within the genus Gardnerella. International Journal of Systematic and Evolutionary Microbiology. 2019;69(3):679–687.
- Gao M, Manos J, Whiteley G, Zablotska-Manos I. Antibiofilm agents for the treatment and prevention of bacterial vaginosis: a systematic narrative review. The Journal of Infectious Diseases. 2024;230(3):e508–e517.
- Cohen CR, Wierzbicki MR, French AL, et al. Randomized trial of Lactin-V to prevent recurrence of bacterial vaginosis. New England Journal of Medicine. 2020;382(20):1906–1915.
- Vodstrcil LA, Muzny CA, Plummer EL, Sobel JD, Bradshaw CS. Bacterial vaginosis: drivers of recurrence and challenges and opportunities in partner treatment. BMC Medicine. 2021;19:194.
- Vodstrcil LA, Plummer EL, Fairley CK, et al. Male-partner treatment to prevent recurrence of bacterial vaginosis. New England Journal of Medicine. 2025;392(10):947–957.
