Gardnerella Vaginalis: Causes, Symptoms, Risks, and Treatment

Authored By: Dr. Jana Lim
Last updated: Jul 25, 2025

Gardnerella vaginalis (G. vaginalis) is a type of bacteria that lives in the vagina and is most commonly linked to bacterial vaginosis (BV), a condition caused by the overgrowth of G. vaginalis along with other bacteria when the natural balance of the vaginal microbiome is disrupted.

Normally, the vagina contains mostly helpful bacteria, especially lactobacilli, which keep it healthy and slightly acidic. When Gardnerella grows too much, it can reduce the number of these helpful bacteria and cause symptoms such as unusual discharge and a strong smell.

If left untreated, it may increase the risk of infections, complications during pregnancy, and other reproductive health issues.

An overgrowth of G. vaginalis usually occurs when the number of protective lactobacilli in the vagina decreases due to biological, behavioural, or environmental factors. This disruption allows G. vaginalis and other bacteria to multiply more easily.

Common contributing factors include:

• Frequent vaginal douching.
• Unprotected sex with multiple partners.
• Use of antibiotics that disturb the vaginal microbiome.
• Hormonal changes, especially during menstruation or pregnancy.

These factors can lower vaginal acidity, weakening the body's natural defences that normally keep G. vaginalis under control.

Although G. vaginalis is not classified as a traditional sexually transmitted infection (STI), sexual activity plays an important role in its transmission and recurrence. It is more common in sexually active individuals and may be influenced by new or multiple sexual partners. However, it can also occur in people with no recent sexual activity.

An overgrowth of G. vaginalis commonly results in BV, which may cause a range of noticeable symptoms. The most frequent signs include:

• Thin, grey or white vaginal discharge
• A strong, fish-like odour, especially after sexual intercourse
• Vaginal itching or irritation
• A burning sensation during urination

However, some individuals may have no symptoms, particularly in the early stages or when bacterial levels are low.

What Are the Risks of Untreated Gardnerella Vaginalis?

If left untreated, an overgrowth of G. vaginalis can increase the risk of several health complications. These may include:

• Greater susceptibility to sexually transmitted infections (STIs) – The imbalance weakens the vagina’s natural defences, making it easier for harmful bacteria and viruses to enter.
• Pregnancy-related issues – Inflammation may affect the uterus and surrounding tissues, increasing the risk of preterm birth and low birth weight.
• Post-surgical infections, particularly following gynaecological procedures – A disrupted balance of vaginal bacteria can raise the risk of infection after procedures such as IUD insertion or abortion.
• Pelvic inflammatory disease (PID) – Bacteria can spread from the vagina into the uterus and fallopian tubes, leading to inflammation and potential long-term complications.

G. vaginalis is diagnosed through a combination of symptom assessment and swab-based clinical tests designed to confirm BV. A vaginal swab is typically used to perform several of the following methods:

• Microscopy – The swab sample is examined under a microscope to look for "clue cells," which are vaginal cells coated with bacteria.
• pH Testing – The swab is used to measure vaginal pH, and a result above 4.5 suggests an imbalance in the vaginal environment.
• Whiff Test – A drop of potassium hydroxide is added to the swab sample; the release of a strong, fishy odour may indicate bacterial overgrowth.
• Nucleic Acid Amplification Tests (NAATs) – This lab-based test detects G. vaginalis DNA with high sensitivity and is often used when more precise identification is required.

An overgrowth of G. vaginalis is typically treated with antibiotics that target the bacterial imbalance causing BV.

Commonly prescribed antibiotics (oral or intravaginal) include:

• Metronidazole
• Clindamycin

In some cases, particularly with recurrent BV, additional strategies may be recommended. These may include the use of probiotics to support the growth of healthy vaginal bacteria or follow-up consultations to explore contributing factors such as sexual activity or hygiene practices.

At ATA Medical, we offer diagnostic testing for bacterial vaginosis caused by G. vaginalis, along with appropriate treatment when required. Our prices are as follows:

We also provide a full range of STI testing and women’s health services. Female doctors are available on request to support your comfort throughout the consultation and testing process.

Contact us to learn more or to book an appointment.

Preventing an overgrowth of G. vaginalis involves supporting the natural balance of bacteria in the vagina and avoiding behaviours that may disrupt it. Key prevention strategies include:

• Avoiding vaginal douching, which can interfere with the vagina’s natural bacterial balance.
• Completing prescribed antibiotic courses fully to help prevent bacterial overgrowth.
• Using condoms during sexual activity to reduce the spread of potentially disruptive bacteria.
• Limiting the number of sexual partners, as frequent changes may influence vaginal health.
• Wearing breathable, cotton undergarments to help keep the area dry and minimise irritation.