Gardnerella Vaginalis

Gardnerella vaginalis is a bacteria that coexists alongside other bacteria in your vagina to keep it infection-free. When too much gardnerella bacteria grows, you can develop an infection called bacterial vaginosis (BV). BV is the most common vaginal infection and can be easily treated with antibiotics.


What is gardnerella vaginalis?

Gardnerella vaginalis is one type of bacteria inside your vagina. It’s part of what’s known as your microbiome or vaginal flora. Your vaginal flora includes different varieties of bacteria and different amounts of these bacteria that keep your vagina healthy. The bacteria coexist in a delicate balance.

When your levels of gardnerella are in balance with the other bacteria, your vaginal flora prevents you from getting infections. If there’s an imbalance and too much gardnerella grows, you can get a vaginal infection called bacterial vaginosis (BV).

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What is the purpose of Gardnerella vaginalis?

When Gardnerella was first discovered in 1955, it was thought of as a “bad” bacteria that caused vaginal infections. The thinking that Gardnerella led to infection was so accepted that people referred to what we now know as BV, a specific kind of vaginal infection, as simply “Gardnerella vaginosis.” People named the infection after the bacteria they thought caused it.

Since then, research has shown that things aren’t so straightforward. People with vaginal infections have Gardnerella bacteria in their vaginas, but people without vaginal infections have Gardnerella, too. This means that Gardnerella alone isn’t to blame for vaginal infections. BV is caused by many other bacteria like atopobium vaginae and megasphera. However, Gardnerella is isolated in the majority of cases.

We now know that Gardnerella plays a role in maintaining a healthy PH, or a healthy amount of acidity, in your vaginal fluid. A healthy vagina has a PH range of 3.8-4.5. It’s considered to have a moderate amount of acid. The bacteria that make up your vaginal flora, including Gardnerella, work to maintain this level of acidity, which is just the right amount of acid for fighting infection. When the acidity levels drop, too much Gardnerella grows, and that’s when an infection can occur.

In other words, Gardnerella's purpose depends on how much you have of it. Having too much Gardnerella bacteria is a sign of BV. Lack of lactobacillus or the wrong composition of lactobacillus creates an imbalance in the presence of Gardnerella, leading to BV. Having the right amount of Gardnerella and lactobacillus means that your vaginal flora is in balance and infection-free.


Where is gardnerella vaginalis located?

Gardnerella lives inside your vagina, as one of many microorganisms that are part of your vaginal flora.


Conditions and Disorders

What are the common conditions and disorders associated with Gardnerella vaginalis?

Gardnerella (a bacteria) is often confused with BV (a specific kind of vaginal infection). And sometimes Gardnerella and BV both are mistaken for sexually transmitted infections (STIs). But Gardnerella isn’t the same as BV, and it isn’t considered a sexually transmitted bacteria (at least not officially).

Is Gardnerella the same as bacterial vaginosis (BV)?

No. But Gardnerella is associated with BV. And having too much Gardnerella in your vaginal fluid is a sign that you have BV.

You get BV when the delicate balance of bacteria that keeps your vaginal flora healthy becomes disturbed. It’s unclear what causes this imbalance. But the amount of two different kinds of bacteria in your vagina lactobacilli bacteria and Gardnerella bacteria – is key.

People with BV have too little lactobacilli bacteria in their vaginas and too much Gardnerella bacteria. Lactobacilli bacteria help keep your vagina acidic. Not having enough lactobacilli bacteria causes your vaginal PH to increase to 4.6 or more, so that your vagina isn’t acidic enough. In this environment, Gardnerella starts to multiply, and other bacteria begin to cling to the Gardnerella bacteria and grow, too. When this happens, you get BV. But Gardnerella alone doesn’t cause BV. An imbalance in your vaginal flora causes BV.

Is Gardnerella vaginalis an STI?

No. Gardnerella isn’t an STI. But it’s a bacteria that’s most likely transmitted sexually. And this can be confusing. Gardnerella isn’t considered a sexually transmitted bacteria, like the bacteria that cause gonorrhea, syphilis or chlamydia, for a few reasons:

  • Having Gardnerella bacteria doesn’t mean you have an infection. Healthy vaginas have Gardnerella bacteria in them. This isn’t the case with other common STIs, where the presence of the bacteria means that you have an infection.
  • People who are not sexually active get BV. People with new sex partners or multiple sex partners often have unhealthy levels of Gardnerella, and these overgrowths are associated with BV. But people who are not sexually active can have unhealthy levels of Gardnerella and BV, too. Sexual activity alone doesn’t seem to cause overgrowths of Gardnerella bacteria or BV. Still, sexual activity can put you at risk for BV.
  • There isn’t an equivalent for sex partners with penises. Other STIs get transmitted regardless of your reproductive anatomy. For example, you can get chlamydia if you have a vagina or if you have a penis. But Gardnerella vaginalis is part of the vaginal flora alone. Gardnerella bacteria has been detected on penises, but it doesn’t occur there naturally. Related, BV infections commonly affect people with vaginas but not people with penises.

Just because Gardnerella isn’t an STI-causing bacteria doesn’t mean that sexual activity isn’t a risk factor when it comes to getting BV. It is. The causes of BV are unknown, but you’re more likely to get an infection if you have multiple sex partners or if you have a new sex partner.

What causes Gardnerella vaginalis?

Gardnerella isn’t something that you can catch. Instead, Gardnerella vaginalis is a natural part of the environment in your vagina. You can get BV if too much Gardnerella grows. Causes of BV are unknown, but people with more sex partners and multiple sex partners are more at risk for getting BV.


Common signs or symptoms that you have an unhealthy amount of Gardnerella vaginalis?

If too much Gardnerella begins to grow, you may start to notice changes in your vaginal discharge that are signs of BV. The fluid from your vagina may:

  • Look off-white, gray or green.
  • Smell fishy, and the odor may be especially strong after sex or during your period.

You can have BV without having any symptoms at all. Whether BV causes symptoms or not, you should see your provider and get treated if you have BV.

Common tests to check for Gardnerella vaginalis?

Your provider can look at your vaginal fluid under a microscope to check for Gardnerella vaginalis bacteria.

Common treatments for unhealthy amounts of Gardnerella?

Untreated BV increases your risk for pregnancy complications, like premature birth and miscarriage. It also puts you at greater risk of contracting STIs. Your provider may prescribe oral or intravaginal antibiotics to return your Gardnerella to healthy levels and resolve your BV.

  • Oral antibiotics. Metronidazole, Secnidazole, Tinidazole.
  • Intravaginal antibiotics. Metronidazole, Clindamycin.


What are some tips to maintain a healthy vaginal flora?

  • Don’t douche. Your vagina does a good job maintaining a healthy amount of bacteria. Douching can create an imbalance among the bacteria in your vagina that can lead to infection.
  • Use condoms or dental dams during sex. Having unprotected sex increases the chance that your vaginal flora will be disrupted and you’ll get BV.
  • Limit your number of sex partners. Having multiple sex partners increases the likelihood you’ll get an infection.

A note from Cleveland Clinic

Don’t be alarmed if you learn that you have Gardnerella vaginalis bacteria. It’s a common type of bacteria that’s supposed to be in your vagina. If your provider tells you that you have an overgrowth of Gardnerella or that you have BV, rest assured that the condition is treatable. A course of antibiotics can get your vaginal flora back to healthy levels within about a week.

Medically Reviewed

Last reviewed on 11/01/2021.

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