If you’ve ever had bacterial vaginosis, you may be familiar with Gardnerella vaginalis, a type of bacteria that’s often associated with dysbiosis (also known as bacterial vaginosis). 

But what is Gardnerella vaginalis? Is there more than one type? Why can Gardnerella wreak havoc in my vagina? And do I always need to get rid of Gardnerella if it’s in my vaginal microbiome?

We explain everything you need to know about this bacterial species below.  

What is Gardnerella?

Gardnerella is a bacteria often found in the vaginal microbiome. Though Gardnerella can sometimes coexist peacefully with other microbes, other times it can over-grow and cause vaginal discomfort or lead to a vaginal infection like bacterial vaginosis.

Like many other things in vaginal healthcare, researchers still don’t understand what causes Gardnerella overgrowth, and the exact downstream issues it causes for people with vaginas. But, by taking an Evvy test, you can help researchers better understand why this microbe can coexist peacefully in the vaginal microbiome versus when it causes active symptoms and other problems such as bacterial vaginosis. 

Let’s go over what we do know about Gardnerella, including Gardnerella vaginalis, based on the current research. 

What are the different species of Gardnerella?

If you’ve had bacterial vaginosis, you’ve likely heard of Gardnerella vaginalis, but did you know there are other species within this group? Currently, there are four named species, which are all closely related:  Gardnerella leopoldii, Gardnerella swidsinskii, Gardnerella piotii, and Gardnerella vaginalis which are all closely related. 

Researchers have been investigating the connection between Gardnerella vaginalis and bacterial vaginosis since 1953.

But it was only in 2019, with the application of whole genome sequencing, that we discovered there were multiple different species of Gardnerella, and the newer species got their names.

This matters because not all Gardnerella are the same. But, as we said above, science is still figuring out what each of these new species actually does in the vagina and how they affect overall vaginal health. 

Most of the research up to 2019 uses the term Gardnerella vaginalis, but with the discovery of these new species, it is unclear how much of this research can be attributed to a specific species rather than the genera overall. 

What does Gardnerella do in the vagina?

Gardnerella is an “indicator species” meaning it is often associated with bacterial vaginosis. 

Gardnerella is present in 98% of women with symptomatic bacterial vaginosis, but it can also be found in 55% of asymptomatic women. This means that you can be in Community State Type IV can be Gardnerella dominant, and not experience symptoms! That being said, Gardnerella dominant microbiomes are more at risk for developing bacterial vaginosis and its typical symptoms including excessive thin, gray or white discharge, fishy odor, and itching.

Is Gardnerella the sole cause of BV?

Back in the 1950s, researchers thought that Gardernella vaginalis alone might cause bacterial vaginosis (“BV”). In some older studies linking Gardnerella vaginalis bacteria and bacterial vaginosis, the condition is called "non-specific vaginitis," which is a term not commonly used anymore, but you may come across it in a internet search rabbit hole (we’ve been there too). However, many studies since then have been trying to figure out which specific species of Gardnerella might be causing symptoms and which might be hanging out peacefully in the vagina—no single species of bacteria is universally present in all vaginas with bacterial vaginosis, making it impossible that Gardnerella is the sole cause of BV.

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Is Gardnerella responsible for your vaginal symptoms? 

Gardnerella and Vaginolysin

We do know that Gardnerella microbes have some special features or genes that could be contributing to symptoms (in science-speak, these genes are called pathogenicity genes). Specifically, Gardnerella can produce a toxin called “vaginolysin.”

In experiments, vaginolysin can directly damage the cells lining the vagina. However, this can only happen if vaginolysin reaches the bottom side, as opposed to the surface, of the cells.

Here’s where things get interesting: some Gardnerella strains found in bacterial vaginosis do not have the genes required to produce vaginolysin, or those genes are mutated somehow. Does that mean some Gardnerella could actually be less harmful or even neutral or protective?

Well, we’re still trying to map out which Gardnerella species and strains produce an active version of this gene and which don’t. 

To further complicate things, not all Gardnerella produce the same amount of vaginolysin and other microbes, like Lactobacillus, can suppress vaginolysin production. 

So, although we know vaginolysin exists, that it can theoretically damage the lining of the vagina if it reaches the right place, and some Gardnerella might produce it given the right conditions, it isn’t a one-size-fits-all explanation of why Gardnerella vaginalis is associated with bacterial vaginosis

Gardnerella and Sialidase

Another pathogenicity gene Gardnerella produces is sialidase. 

Sialidase is an enzyme that breaks down the mucus layer covering the vaginal wall. We know that levels of sialidase in vaginal secretions are associated with a shift from a Lactobacillus dominant microbiome to a more diverse microbiome

Sialidase and biofilms 

If you’ve ever dealt with chronic bacterial vaginosis, yeast infections, or any vaginal infections, you may have heard of a biofilm.

Biofilms are three-dimensional structures bacteria form that make it hard to clear an infection, including vaginal infections like bacterial vaginosis

It is hypothesized that sialidase is needed to break down the mucus layer and produce biofilms.

Gardnerella is not the only bacteria that can produce sialidase: Prevotella and Mobiluncus can as well. And, different species and strains of Gardnerella produce varying amounts of sialidase

Gardnerella and Biofilms

This leads us to the last of the three Gardnerella pathogenicity genes we are going to cover: biofilms. As we said above, biofilms are 3D clumps of bacteria that make it super hard to get rid of bacterial vaginosis with just antibiotics alone, leading to persistent vaginal symptoms like excessive vaginal discharge and odor. 

Gardnerella makes excellent biofilm scaffolding and it can grab onto the lining of the vagina. Gardnerella biofilms also make great homes for other bacteria like Prevotella, Fannyhessae, and Mobiluncus.  So once Gardnerella is established in a biofilm it is easier for these other bacteria to colonize and since they are all living together in the same biofilm, they are all equally hard to get rid of. It’s a party, but not the kind we want to be invited to. 

Can Gardnerella be causing my recurrent UTIs?

Not directly, but it can make it easier for E. coli to cause infections. E. coli is the most common cause of UTIs

Like BV, E. coli UTIs can come back again and again. There are a couple of reasons this can happen, but one thing E. coli can do is hang out inside bladder cells (these are called intracellular bacterial community or IBCs). Hiding out in these cells protects E. coli from the immune system allowing it to chill out until the time is right to re-infect the bladder. 

Recent research has shown that if Gardnerella gets into the bladder it can cause these E. coli IBCs to become active, essentially luring E. coli out of its hiding place.

The result is a UTI flare-up. So while Gardnerella alone does not cause UTIs, it can be the trigger for an episode. 

I have Gardnerella in my Evvy sample—does it always need to be treated?

Everything treatment-related should be a direct conversation with a healthcare provider such as your OB-GYN. Evvy tests for all bacteria and fungi that can impact the vaginal microbiome, making it an incredibly powerful tool if you believe Gardnerella may be present down there.

Other than detecting Gardnerella, a provider will likely also want to discuss what other microbes are present and what your symptoms are in order to determine your best care options.

If you are eligible for Evvy Care and you have Gardnerella in your results, an Evvy-affiliated provider can provide you with a care plan especially targeted towards reducing Gardnerella and building back the more protective microbes.

According to clinical guidelines, the presence of Gardnerella alone doesn’t need to be treated in the absence of any vaginal symptoms or discomfort.

If you do have symptoms like abnormal thin, gray white discharge, discomfort, itching, or soreness, and Gardnerella is in your sample, it's important to bring up these details to a physician or in the health history form that comes with every Evvy test. 

Remember how we said that taking an Evvy test can help further the research on whether or not Gardnerella acts in the vaginal microbiome depending on who its neighbors are?

We hope that the metagenomic sequencing we use will help give us insights into Gardnerella and other microbes to provide you and other people with vaginas the best, most personalized care pathways available. 

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