Bacterial Vaginosis (Gardnerella vaginalis)
Overview
Plain-Language Overview
Bacterial Vaginosis (BV) is a common vaginal infection that affects the female reproductive system. It occurs when the normal balance of bacteria in the vagina is disrupted, leading to an overgrowth of harmful bacteria like Gardnerella vaginalis. This imbalance can cause symptoms such as a thin, grayish vaginal discharge and a fishy odor, especially after intercourse. BV can increase the risk of other infections and complications during pregnancy. It is important to recognize these symptoms as they indicate an alteration in the vaginal environment.
Clinical Definition
Bacterial Vaginosis (BV) is a vaginal dysbiosis characterized by a reduction in lactobacilli and an overgrowth of anaerobic bacteria, predominantly Gardnerella vaginalis. This shift disrupts the normal acidic vaginal pH, increasing it above 4.5, which facilitates colonization by pathogenic bacteria. BV is the most common cause of vaginal discharge in women of reproductive age and is associated with increased risk of pelvic inflammatory disease, preterm labor, and susceptibility to sexually transmitted infections. The condition is often asymptomatic but can present with characteristic malodorous discharge. The pathogenesis involves biofilm formation on the vaginal epithelium by Gardnerella and other anaerobes, leading to chronic colonization and inflammation.
Inciting Event
Sexual activity introducing anaerobic bacteria into the vaginal environment.
Disruption of vaginal flora by douching or antibiotic therapy.
Hormonal changes such as those during menstruation or pregnancy altering vaginal pH.
Latency Period
Symptoms typically develop within days to 1 week after disruption of normal flora.
There may be a variable asymptomatic period before clinical presentation.
Diagnostic Delay
Symptoms are often mild or absent, leading to underreporting.
Misattribution to yeast infection or other vaginitis delays correct diagnosis.
Lack of routine microscopic examination or use of inappropriate tests can delay diagnosis.
Clinical Presentation
Signs & Symptoms
Thin, homogenous vaginal discharge that is gray or white in color is the hallmark symptom.
Fishy vaginal odor often worsens after intercourse due to alkaline semen altering vaginal pH.
Mild vaginal itching or irritation may be present but is less common than in candidiasis.
History of Present Illness
Patients commonly report thin, gray-white vaginal discharge with a fishy odor especially after intercourse.
Vaginal itching or irritation is usually mild or absent.
Symptoms may fluctuate with the menstrual cycle and worsen after sexual activity or douching.
Past Medical History
History of recurrent bacterial vaginosis or other vaginal infections increases risk.
Prior use of broad-spectrum antibiotics can predispose to flora disruption.
Use of intrauterine devices or recent gynecologic procedures may be relevant.
Family History
There is no well-established heritable pattern or familial syndrome associated with bacterial vaginosis.
Family history is generally not contributory to risk or presentation.
Physical Exam Findings
Thin, gray-white vaginal discharge coating the vaginal walls is characteristic of bacterial vaginosis.
Vaginal mucosa appears normal without significant erythema or edema, distinguishing it from infectious vaginitis.
Fishy odor is often noted when the discharge is present, especially after adding potassium hydroxide (KOH).
Diagnostic Workup
Diagnostic Criteria
Diagnosis of bacterial vaginosis is established using Amsel criteria, requiring at least three of the following: a homogeneous, thin, grayish vaginal discharge, vaginal pH greater than 4.5, a positive whiff test (fishy odor on adding KOH), and the presence of clue cells on microscopic examination of vaginal fluid. Alternatively, the Nugent score from Gram stain of vaginal smear quantifies bacterial morphotypes, with a score of 7-10 confirming BV. These diagnostic methods focus on identifying the characteristic bacterial imbalance and clinical features.
Pathophysiology
Key Mechanisms
Disruption of normal vaginal flora with depletion of Lactobacillus species leads to overgrowth of anaerobic bacteria, primarily Gardnerella vaginalis.
Increased vaginal pH (>4.5) facilitates proliferation of anaerobic bacteria and reduces protective acidic environment.
Production of amines by anaerobic bacteria causes the characteristic fishy odor and alters vaginal secretions.
Biofilm formation by Gardnerella vaginalis on vaginal epithelial cells promotes bacterial persistence and resistance to host defenses.
| Involvement | Details |
|---|---|
| Organs | Vagina is the organ involved, where the imbalance of normal flora leads to bacterial vaginosis and its clinical manifestations. |
| Tissues | Vaginal mucosa is the primary tissue affected in bacterial vaginosis, showing disruption of normal lactobacilli-dominated flora. |
| Cells | Epithelial cells of the vaginal mucosa are disrupted in bacterial vaginosis, facilitating overgrowth of anaerobic bacteria. |
Polymorphonuclear leukocytes are typically decreased in bacterial vaginosis, reflecting a lack of significant inflammation. | |
| Chemical Mediators | Volatile amines produced by anaerobic bacteria cause the characteristic fishy odor in bacterial vaginosis. |
pH elevation in vaginal secretions above 4.5 promotes overgrowth of Gardnerella vaginalis and other anaerobes. |
Treatments
Pharmacological Treatments
Metronidazole
- Mechanism:
Disrupts DNA synthesis in anaerobic bacteria including Gardnerella vaginalis by forming toxic metabolites.
- Side effects:
Metallic taste
Nausea
Disulfiram-like reaction with alcohol
- Clinical role:
First-line
Clindamycin
- Mechanism:
Inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, effective against anaerobic bacteria.
- Side effects:
Diarrhea
Clostridioides difficile colitis
Allergic reactions
- Clinical role:
First-line
Non-pharmacological Treatments
Avoidance of douching to maintain normal vaginal flora and prevent disruption of the vaginal microbiome.
Use of condoms to reduce risk of recurrent bacterial vaginosis by limiting bacterial exchange.
Prevention
Pharmacological Prevention
Metronidazole gel or oral therapy can be used prophylactically in women with recurrent bacterial vaginosis.
Clindamycin vaginal cream is an alternative prophylactic agent to maintain normal vaginal flora.
No routine antibiotic prophylaxis is recommended for asymptomatic women without recurrent infections.
Non-pharmacological Prevention
Avoidance of douching to preserve normal vaginal flora and prevent disruption of protective lactobacilli.
Use of condoms to reduce exposure to semen and sexually transmitted pathogens that alter vaginal pH.
Limiting multiple sexual partners decreases risk of bacterial vaginosis by reducing exposure to diverse vaginal microbiota.
Outcome & Complications
Complications
Increased susceptibility to HIV infection due to disruption of normal vaginal flora and mucosal barrier.
Pelvic inflammatory disease (PID) resulting from ascending infection facilitated by bacterial vaginosis.
Postoperative infections such as endometritis after gynecologic surgeries or procedures.
| Short-term Sequelae | Long-term Sequelae |
|---|---|
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Differential Diagnoses
Bacterial Vaginosis (Gardnerella vaginalis) versus Vulvovaginal Candidiasis
Bacterial Vaginosis (Gardnerella vaginalis) | Vulvovaginal Candidiasis |
|---|---|
Polymicrobial imbalance with predominance of Gardnerella vaginalis and anaerobes | Overgrowth of Candida albicans or other Candida species |
Clue cells on saline wet mount with positive whiff test | Presence of budding yeast and pseudohyphae on wet mount or KOH prep |
Thin, homogenous, grayish vaginal discharge with fishy odor | Intense vulvar pruritus and thick, curd-like vaginal discharge |
Bacterial Vaginosis (Gardnerella vaginalis) versus Trichomoniasis
Bacterial Vaginosis (Gardnerella vaginalis) | Trichomoniasis |
|---|---|
Bacterial overgrowth dominated by Gardnerella vaginalis | Infection with motile Trichomonas vaginalis protozoa |
Clue cells without motile organisms on wet mount | Motile trichomonads seen on wet mount microscopy |
Thin, grayish vaginal discharge with minimal vulvar irritation | Frothy, yellow-green vaginal discharge with vulvar irritation |
Bacterial Vaginosis (Gardnerella vaginalis) versus Chlamydia trachomatis Infection
Bacterial Vaginosis (Gardnerella vaginalis) | Chlamydia trachomatis Infection |
|---|---|
Polymicrobial bacterial imbalance with Gardnerella vaginalis predominance | Intracellular gram-negative obligate intracellular bacterium Chlamydia trachomatis |
Negative NAAT for Chlamydia trachomatis with clue cells on microscopy | Positive nucleic acid amplification test (NAAT) for Chlamydia trachomatis |
Typically malodorous vaginal discharge without cervical inflammation | Often asymptomatic or mucopurulent cervical discharge with possible pelvic pain |
Bacterial Vaginosis (Gardnerella vaginalis) versus Gonorrhea
Bacterial Vaginosis (Gardnerella vaginalis) | Gonorrhea |
|---|---|
Polymicrobial bacterial imbalance dominated by Gardnerella vaginalis | Infection with gram-negative diplococcus Neisseria gonorrhoeae |
Negative NAAT for Neisseria gonorrhoeae with clue cells on microscopy | Positive culture or NAAT for Neisseria gonorrhoeae |
Thin, homogenous vaginal discharge without cervical purulence | Purulent cervical discharge and possible pelvic inflammatory disease |
Bacterial Vaginosis (Gardnerella vaginalis) versus Atrophic Vaginitis
Bacterial Vaginosis (Gardnerella vaginalis) | Atrophic Vaginitis |
|---|---|
Reproductive-age woman with normal estrogen levels | Postmenopausal estrogen deficiency or hypoestrogenic state |
Malodorous, thin vaginal discharge with minimal irritation | Vaginal dryness, irritation, and dyspareunia without malodorous discharge |
Presence of clue cells and decreased lactobacilli | Absence of clue cells and normal vaginal flora with low lactobacilli |