Are you more of a visual learner? Check out our online video lectures and start your infectious diseases course now for free!

gardnerella vaginalis

Image: “Microscopic view of Gardnerella vaginalis, magnified 400x.” by Dr. F.C. Turner – Photographed myself using Olympus BX50 microscope on the Department of Pathology, University Medical Center Groningen, The Netherlands. License: Public Domain

Definition and Background of Gardnerella Vaginalis

Gardnerella vaginalis is a pleomorphic, gram-variable (mostly gram-negative), facultative nonmotile anaerobic rod. Overgrowth of this bacteria is the most frequent cause of vaginitis in women (90% of vulvovaginitis) and causes epidemiological concern in males (urethritis).

Advanced microbiology technologies, including the electron microscope, improved laboratory equipment, and better testing methods (isolation and identification of bacteria), mean that the term ‘nonspecific vaginitis’ lost its meaning. The condition’s specific cause was detected and can be described in detail.

Typically, G. vaginalis is transmitted through sexual infection. Some clinical researchers suggest that the rectum may be inhabited with G. vaginalis, so the bacteria can travel from the rectum to the genitals, resulting in self-infection.

The healthy female vagina contains a high concentration of lactobacilli that maintain the vagina’s acidic pH. G. vaginalis infection reduces the lactobacilli population, thereby increasing the vaginal pH.

Advanced stages of the infection may lead to severe consequences in the form of pelvic inflammatory disease.

Etiology of Gardnerella Vaginalis

  • Bacterial vaginitis (BV, vulvovaginitis) develops from infection with different anaerobic bacteria, including B. vaginalis, and is a result of their interaction: Lactobacillus, Prevotella; anaerobes: Mobiluncus, Bacteroides, Peptostreptococcus, Fusobacterium, Veillonella Eubacterium, Mycoplasma hominis, Ureaplasma urealyticum, Streptococcus viridans, and Atopobium vaginae
  • An impaired immune response may trigger BV development
  • Lower estrogen production of the host
  • High frequency of intercourse
  • Multiple sex partners
  • Use of IUD
  • Pregnancy
  • Long-term antibiotic therapy
  • Douching
  • Promiscuity in sexual contacts

Epidemiology of G. Vaginalis

BV is a very common condition. In the US, 29.8% of the female population was diagnosed with BV with a Gram stain in vaginal fluid. Susceptibility increases amidst those ones who are non-white, practice douching, have numerous sexual partners, and have sex with women. Smoking and obesity are also risk factors. It occurs mainly in women of reproductive age. Patients with HIV are infected with G. vaginalis and develop BV twice as frequently.


G. vaginalis is very common worldwide, especially in countries with a humid and hot climate; thus, over 50% of women infected with G. vaginalis are in sub-Saharan Africa; they also have a higher of contracting HIV.

Presentation of G. Vaginalis


  • Foul vaginal odor (‘fishy odor’), especially after sexual intercourse (one of the most distinguishing features of BV)
  • An increased amount of grayish vaginal discharge, which is non-painful and non-inflammatory.
  • Grayish vaginal discharges
  • Dysuria
  • Vulvar irritation (itchiness)

Physical examination

The labia, introitus, cervix, and cervical discharge appear normal; however, there may be signs of cervicitis. Vaginal walls produce enhanced light reflex without pronounced inflammation. The vaginal mucosa is covered with gray, watery, homogenous discharges.

Differential Diagnosis of G. Vaginalis


This is a vaginal yeast infection caused by candida albicans. Patients present with vaginal redness, itching, and curd-like discharges. The cervix usually appears normal, with no inflammation.


This describes the condition when there are visible purulent or mucopurulent endocervical discharges in the cervical canal, and the cervix bleeds easily on touch.

Chlamydial genitourinary infections

These are caused by the bacterium called Chlamydia and is the leading cause of infertility in US women. Chlamydia affects the urethra, salpinges, uterus, nasopharynx, and epididymis, causing unpleasant vaginal discharges, vaginal bleeding between periods, lower abdominal pain, sometimes fever if pelvic organs are involved in inflammation, dyspareunia, and rectal discharges after anal intercourse.


The so-called ‘clap’ is caused by the bacterium neisseria gonorrhoeae and presents with thin or thick, purulent, and mildly odorous vaginal discharges, sometimes minimal or no discharges, dyspareunia, mild lower abdominal pain, and bleeding between periods.

Herpes simplex

Herpes simplex is caused by the virus of the herpes family, and the signs are ulceration of the penis or vagina followed by insignificant discharges and itchiness of affected zones. There might be enlarged local lymphatic nodes as well as fever and malaise.


This condition causes gray, yellow, or green foul-smelling discharge from the vagina urethra, painful urination, and intercourse, dysuria, vaginal bleeding after intercourse or unrelated to menses, genital itchiness, and a burning sensation.

Table: Differential Diagnosis of Vaginitis

Clinical Elements Bacterial vaginosis Trichomoniasis Vaginal candidiasis
Symptoms Vaginal odor + +/-
Vaginal discharge Thin, gray, homogenous Green-yellow White, curd-like
Vulvar irritation +/- + +
Dyspareunia +
Signs Vulvar erythema +/-
Bubbles in vaginal fluid + +/-
Strawberry cervix +/-
Microscopy Saline wet mount
Clue cells +
Motile protozoa +
Pseudohyphae +
Whiff test + +/-
pH >4.5 >4.5 < 4.5

Diagnosis of G. Vaginalis

Laboratory studies

Microscopic examination of the vaginal discharge will have these characteristics:

  • clue cells – vaginal epithelial cells with attached bacteria on their surfaces, edges of the cells are stubbed, and ‘peppered’ with coccobacilli
  • pH is greater than 4,5
  • Vaginal discharge is gray, watery, and homogenous
  • Minimal polymorphonuclear leukocytes (PMNs)-1 per one vaginal epithelial cell
  • Catalase-negative, oxidase-negative, and facultative anaerobe

The whiff test is positive in 90% of cases. This test can be conducted by mixing the vaginal fluid with a drop of KOH on a microscope slide to detect the presence of amine, which is produced by anaerobic bacterial metabolism.

Microscopic evaluation of the bacteria flora is informative when looking for evidence of changes in the overall bacterial predominance. Thus, lactobacilli (large gram-positive rods) are predominant normally. In BV, coccobacilli dominate over any other microflora (anaerobes), and there is a reduced lactobacilli population.

Vaginal cultures can exclude other pathogenic growth apart from G. vaginalis, namely trichomonas species, C. trachomatis, and N. gonorrhea. G. vaginalis is detected in 100% of BV and 70% of asymptomatic BV.


Colposcopy reflects clean, translucent mucus in external cervical os and opaque vaginal contents in the rear vaginal vault. ‘Spotted’ images, visible after a Schiller test, are pathognomic colposcopic features of G. vaginalis infection.

Treatment of Gardnerella Vaginalis

The treatment of G. vaginalis has to be prescribed appropriately based on the results of the clinical examination and cytological testing. Antibacterial therapy is a first-line pharmacological treatment. For G. vaginalis, doctors recommend metronidazole, metronidazole gel, or clindamycin cream.


Medication Duration
Metronidazole 500 mg, orally twice per day 7 days
Metronidazole gel 0,75%, one full applicator intravaginally (5g), once a day 5 days
Clindamycin cream 2% one full applicator intravaginally (5g) at bedtime 5 days

Patients taking treatment with metronidazole have to refrain from drinking alcohol during the entire course and 24 hours afterward; clindamycin cream softens the latex of condoms and diaphragms for 5 days after use.

Restricting sexual activity may be recommended depending on the severity and nature of the illness.

Surgical intervention is not required for G. vaginalis infections.

Patients frequently ask

Is G. vaginalis in men possible?

G. vaginalis is rare in men. The risk factors for males include being immunocompromised, having anatomical genitourinary abnormalities, or being alcoholics. It is not considered a sexually transmitted infection, but it may be transmitted during intercourse. If Gardnerella is diagnosed, men should also take a standardized treatment as a precaution to avoid retransmission to the partner.

Is G. vaginalis a sexually transmitted disease?

G. vaginalis is not considered a sexually transmitted disease, but sexual contact may induce this condition in some patients. An increased number of sexual partners in a month or having an increased number of lifetime sexual partners may predispose the condition.

Learn. Apply. Retain.
Your path to achieve medical excellence.
Study for medical school and boards with Lecturio.
Rate this article
1 Star2 Stars3 Stars4 Stars5 Stars (Votes: 1, average: 5.00)