Conditions, Cystitis

The Vaginal Bacterium That Can Trigger UTIs

Researchers have identified a common vaginal bacterium that may trigger UTIs.

This could explain why recurring episodes of UTIs are often triggered by sexual intercourse.

The bacterium called Gardnerella vaginalis may not only be responsible for triggering UTIs, it may also be a contributor to more serious kidney infections.

About Gardnerella Vaginalis

Gardnerella vaginalis is a bacterium that can be found in the vagina. It may be present in healthy vaginas in small numbers but in larger numbers it is associated with bacterial vaginosis (BV).

Bacterial vaginosis can lead to unpleasant symptoms such as itchiness, burning and swelling.

An overgrowth of Gardnerella vaginalis may signal an imbalance of bacteria in the vagina (dysbiosis).

Especially during intercourse, this bacterium could be transferred to the urethra and travel into the bladder.

Gardnerella vaginalis’ Effect on the Bladder

Normally, UTIs are thought to be caused by bacteria entering the bladder from the bowel. The most common pathogen responsible for UTIs is E. Coli.

It was believed that recurrence of UTIs occurs after re-infection of a pathogen entering the bladder from outside. Now we know that pathogens can in fact hide in our bladder cells and under biofilms from where they can re-enter the bladder and cause infection.

In a study done on mice, the bacterium Gardnerella vaginalis as such does not cause urinary tract infections and is eliminated from the bladder within a day.

Instead, they seem to damage the cells on the surface of the bladder lining, allowing intracellular pathogens to multiply and re-infect the urinary tract.

In mice, Gardnerella vaginalis in the bladder also made it more likely for urinary pathogens to travel up to the kidneys and cause more serious infections and damage.

Sexual Cystitis

Gardnerella vaginalis may be one of the triggers of sexual cystitis (urinary tract infections caused by sexual intercourse).

If Gardnerella vaginalis is present in large numbers in the vagina, it may well be transferred to the bladder opening during intercourse.

In women with a history of UTIs, this could explain why recurrent UTIs are triggered by intercourse.

Therapeutic Significance

  • When a lab test shows up positive for Gardnerella vaginalis, it may not just be contamination of the sample from the vagina but may hint at the mechanism by which recurrent UTIs are triggered (always ask to see you lab results in detail).
  • If you suffer from bacterial vaginosis as well as UTIs, there may well be a connection.
  • A healthy vagina should be high in the bacterium Lactobacillus Crispatus. Restoring balance of the vaginal flora should be part of any treatment plan.
  • Gardnerella vaginalis does respond to antibiotics but not the same kind as urinary pathogens. Bearing in mind that common antibiotics could upset the vaginal flora further.
  • Through genetic sequencing it is possible to screen bacteria in an on our bodies. Commercial tests for sequencing the vaginal flora are available from UBiome.
  • Ideally, the vaginal flora should be high in Lactobacilli (especially Crispatus) and low in Gardnerella vaginalis.

Now I’d like to hear from you: are you suffering from UTIs and BV? Do you always seem to end up with an UTI after intercourse? Let me know in the comments!

Pin it for later:


EMJ Vaginal Bacterium Linked to Recurrent Urinary Tract Infections April 2017

Science Daily Vaginal bacteria can trigger recurrent UTIs, study shows March 2017


  • Reply

    Lucy-May Galbraith

    May 8, 2017

    It sounds like this may have caused my kidney abscess & septicaemia! Hopefully now that they’ve figured this out they might find a way to treat it better than just regular antibiotics (they just masked the symptoms for me) so that people don’t suffer like I did.

    • Reply


      May 8, 2017

      Thanks for sharing – I hope you got it sorted in the end? Yes, I hope so too but it could be years until it gets into the medical textbooks. But fingers crossed!

  • Reply


    February 18, 2018

    I have been suffering with a kidney infection for almost 2 weeks on 2 different antibiotics with no relief. Finally my culture showed Gardnerella and they switched me to Flagyl hopefully that takes care of my kidney infection too.

  • Reply


    April 12, 2018

    If I think I’m experiencing this, what medications do they use to treat this? What do I tell my doctor?

  • Reply

    M Wilson

    April 24, 2018

    Hi there,

    I have suffered from recurrent UTIs, BV and thrush for over nine years now. In fact, I always have one, the other or all three. It’s been pretty miserable and I’ve been unable to have sex for the last two years due to pain during and after. Last year I was diagnosed with Interstitial cystitis by a urologist who performed no tests on me. This was frustrating as I have spent most of these years investigating what the problem may be, and the pain seems to be urethral rather than abdominal or pelvic which has made me suspect for a long time the UTIs are a result of the imbalance of flora in my vagina. I feel like I have exhausted every pathway, listened to everyone’s advice and I am so tired of being told to wear cotton pants, wipe front to back and drink some cranberry as believe me, if I’ve heard of it I am doing it. Would be really interested to hear of any more information or help you have on this topic as nobody seems to be able to help. I have found short term treatments to symptoms but nothing to diagnose or treat the root cause of the problem.

    • Reply


      April 24, 2018

      Hi, I’m really sorry you’re suffering, I know what it’s like as I’ve had very similar issues. It’s hard to say what’s going on exactly without knowing more about your health history. A general imbalance of bacteria/microbes, mainly in the gut, may be behind issues like that and it’s definitely something I’d personally look into.
      An imbalance of urogenital bacteria could sure be an issue, as these help protect the urethra. But again, the gut plays a big role in all of this.

  • Reply

    M Wilson

    April 24, 2018

    Thanks for your response, Layla. Am trialling the anti Candida diet at the moment and I know there’s a lot more possibilities to explore!

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