2.1 Vulvovaginitis: Bacterial Vaginosis, Candidiasis & Trichomoniasis
Key Takeaways
Normal vaginal pH ranges from 3.8 to 4.5, maintained by lactic acid- and hydrogen peroxide-producing Lactobacillus species that colonize estrogen-stimulated squamous epithelium.
Bacterial vaginosis is diagnosed clinically using Amsel criteria (at least 3 of 4: thin homogeneous discharge, pH >4.5, positive whiff test, clue cells >20%) and treated with oral metronidazole 500 mg twice daily for 7 days or topical therapies.
Vulvovaginal candidiasis presents with normal pH (3.8-4.5), negative whiff test, and pseudohyphae/blastospores on 10% KOH; uncomplicated cases respond to single-dose oral fluconazole 150 mg, while azole-resistant C. glabrata requires intravaginal boric acid.
CDC advises against oral fluconazole in pregnancy because even a single 150 mg dose has been linked to spontaneous abortion and congenital anomalies; 7-day topical azole regimens are recommended.
Trichomoniasis is diagnosed with high sensitivity using NAAT; updated CDC guidelines mandate oral metronidazole 500 mg twice daily for 7 days (superseding the single 2 g dose) along with expedited partner therapy.
Vulvovaginitis: Bacterial Vaginosis, Candidiasis & Trichomoniasis
Vulvovaginitis represents a leading reason women seek outpatient gynecologic care. Vaginal health relies on a homeostatic ecosystem governed by estrogen, glycogen, and hydrogen peroxide-producing Lactobacillus species (mainly L. crispatus and L. jensenii). These commensals maintain an acidic vaginal pH between 3.8 and 4.5, inhibiting pathogens. Physiologic leukorrhea consists of squames, transudate, and lactobacilli, presenting as clear or white, odorless discharge with pH <= 4.5 and no inflammatory leukocytes. When disrupted, pathological vaginitis results. The three predominant causes are Bacterial Vaginosis (BV), Vulvovaginal Candidiasis (VVC), and Trichomoniasis.
Important
Collect diagnostic secretions from lateral vaginal walls using a non-lubricated speculum. Avoid cervical mucus; cervical secretions are naturally alkaline (pH > 7.0) and produce false-positive elevations on vaginal pH testing.
Differential Diagnosis Matrix
Differentiating vulvovaginitis requires integrating physical findings, vaginal pH, the 10% potassium hydroxide (KOH) whiff test, and microscopy.
| Diagnostic Parameter | Bacterial Vaginosis (BV) | Vulvovaginal Candidiasis (VVC) | Trichomoniasis |
|---|---|---|---|
| Etiology | Polymicrobial dysbiosis (Gardnerella, anaerobes) | Candida albicans (85–90%), C. glabrata | Trichomonas vaginalis (flagellated protozoan) |
| Vaginal pH | Elevated (>4.5, typically 5.0–5.5) | Normal acidic (3.8–4.5) | Markedly elevated (>4.5, often 5.5–6.5) |
| Discharge | Thin, homogeneous, gray-white, adherent | Thick, white, curdy ("cottage cheese"), adherent | Copious, frothy, yellow-green, malodorous |
| Whiff Test | Positive (fishy amine odor with 10% KOH) | Negative | Frequently positive |
| Microscopy | Clue cells (>20%), absent lactobacilli, few WBCs | Pseudohyphae and budding yeast on 10% KOH | Motile flagellated trichomonads, WBCs >10/HPF |
| Primary Symptoms | Fishy malodor (worse post-coitus or menses) | Intense vulvar pruritus, burning, dyspareunia | Copious discharge, irritation, postcoital spotting |
| Cervical Exam | Normal, non-inflamed | Normal or mild erythema | Colpitis macularis ("strawberry cervix" in 2–5%) |
Bacterial Vaginosis (BV)
Bacterial vaginosis is a non-inflammatory dysbiosis marked by lactobacilli depletion and overgrowth of anaerobes, including Gardnerella vaginalis, Atopobium vaginae, Prevotella, and Mobiluncus. Microbial decarboxylases convert amino acids into volatile amines (putrescine, cadaverine), generating a distinct fishy odor.
Diagnostic Criteria
Clinical diagnosis requires at least three of four Amsel criteria:
- Thin, homogeneous, gray-white discharge adhering smoothly to vaginal walls.
- Vaginal pH greater than 4.5.
- Positive whiff test (fishy amine odor upon adding 10% KOH to secretions).
- Clue cells accounting for >=20% of vaginal epithelial cells on saline wet mount (squamous cells stippled with adherent bacteria obscuring borders).
In specialized research settings, the Gram stain-based Nugent score serves as the gold standard (scored 0–10: 0–3 normal Lactobacillus flora; 4–6 intermediate; 7–10 bacterial vaginosis).
Pharmacotherapy
Treatment is indicated for all symptomatic women, and for asymptomatic patients undergoing surgical abortion or upper tract instrumentation.
- First-Line Regimens: Oral metronidazole 500 mg twice daily for 7 days; intravaginal metronidazole 0.75% gel, one applicator (5 g) daily at bedtime for 5 days; or intravaginal clindamycin 2% cream, one applicator (5 g) at bedtime for 7 days.
- Clinical Considerations: The 2021 CDC guidelines state that abstaining from alcohol while taking metronidazole is unnecessary, because the disulfiram-like reaction is not supported by evidence (older labeling still carries the warning). Clindamycin cream is oil-based and can weaken latex condoms and diaphragms for 5 days after use. CDC 2021 did not recommend routine partner treatment, but after a 2025 randomized trial nearly halved recurrence, ACOG (October 2025) supports offering concurrent treatment to the male partner of a patient with recurrent BV in a monogamous relationship: oral metronidazole 400 mg twice daily plus 2% clindamycin cream applied to the penis twice daily, both for 7 days.
Vulvovaginal Candidiasis (VVC)
Vulvovaginal candidiasis affects up to 75% of women. Candida albicans accounts for roughly 90% of infections, with non-albicans species such as Candida glabrata causing the remainder.
Classification & Diagnostics
VVC is divided into uncomplicated and complicated presentations:
- Uncomplicated VVC: Sporadic, mild-to-moderate episodes caused by C. albicans in healthy, non-pregnant, immunocompetent hosts.
- Complicated VVC: Recurrent infections (>=4 episodes in 12 months), severe inflammation (edema, fissures, excoriations), non-albicans species, or occurring with uncontrolled diabetes, immunosuppression, or pregnancy.
Microscopy reveals budding blastospores and branching pseudohyphae on 10% KOH prep. Vaginal pH remains normal (3.8–4.5), and the whiff test is negative.
Treatment Strategies
- Uncomplicated VVC: Oral fluconazole 150 mg single dose, or short-course topical azoles (such as miconazole 2% cream or clotrimazole 1% cream for 7 days).
- Recurrent VVC: Oral fluconazole 150 mg every 72 hours for 3 doses (days 1, 4, 7), followed by weekly maintenance fluconazole 150 mg for 6 months.
- Non-albicans (C. glabrata): Often fluconazole-resistant. CDC recommends a longer (7–14 day) course of a non-fluconazole azole first; for recurrence or treatment failure, use intravaginal boric acid 600 mg in a gelatin capsule once daily for 21 days.
- Pregnancy Considerations: Oral fluconazole is contraindicated due to miscarriage and teratogenicity risks. Only 7-day topical azoles are permitted. Boric acid is strictly contraindicated in pregnancy and fatal if ingested orally.
Trichomoniasis
Trichomonas vaginalis is a sexually transmitted, flagellated anaerobic protozoan infecting the squamous epithelium of the vagina, urethra, and Skene's glands.
Clinical Presentation & Diagnostics
Patients report copious, malodorous, purulent, yellow-green frothy discharge, vulvar irritation, dysuria, and postcoital bleeding. Speculum examination may reveal cervical petechiae ("strawberry cervix"). Vaginal pH is elevated (>4.5, typically 5.5–6.5).
While wet mounts identify motile trichomonads, sensitivity is poor (50–60%). Nucleic Acid Amplification Testing (NAAT) is the gold standard, demonstrating sensitivity and specificity above 95–100%.
Treatment & Partner Management
- Updated CDC Regimen: Oral metronidazole 500 mg twice daily for 7 days. Randomized trials confirmed this 7-day course achieves superior cure rates in women compared to the historic single 2 g dose. Tinidazole 2 g orally in a single dose is an alternative.
- Expedited Partner Therapy (EPT): All sexual partners should be treated concurrently to prevent reinfection. Patients should abstain from intercourse until they and their partners have completed treatment and symptoms have resolved.
- Rescreening: Repeat NAAT screening is mandatory 3 months after completing therapy due to high reinfection rates.
A 28-year-old female presents with a 4-day history of an off-white, thin vaginal discharge accompanied by a prominent fishy odor that worsens following sexual intercourse. She denies vulvar pruritus or dyspareunia. Speculum examination reveals a thin, homogeneous discharge coating the vaginal walls without cervical erythema. Point-of-care testing reveals a vaginal pH of 5.2 and a positive amine whiff test on 10% KOH. Saline microscopy demonstrates clue cells comprising 35% of squamous epithelial cells and absent lactobacilli. What is the most appropriate first-line pharmacotherapeutic regimen for this patient?
Oral fluconazole 150 mg in a single dose
Oral metronidazole 500 mg twice daily for 7 days
Intravaginal boric acid capsules 600 mg daily for 14 days
Intramuscular ceftriaxone 500 mg in a single dose
A 34-year-old woman returns to the clinic with persistent vulvar burning and dyspareunia. She completed two standard courses of oral fluconazole over the past 2 months with no symptom relief. Point-of-care testing reveals a vaginal pH of 4.2 and a negative whiff test. Microscopic evaluation with 10% KOH demonstrates budding yeast blastospores without pseudohyphae. Vaginal fungal culture confirms Candida glabrata infection. What is the most appropriate therapy for this patient?
Oral metronidazole 500 mg twice daily for 7 days, with treatment of her sex partner
Oral fluconazole 150 mg every 72 hours for 3 doses, then weekly for 6 months
Intramuscular benzathine penicillin G 2.4 million units as a single dose
Intravaginal boric acid 600 mg in a gelatin capsule nightly for 21 days
A 24-year-old sexually active woman presents for an annual well-woman examination. She reports mild postcoital spotting and yellowish vaginal discharge. Speculum examination demonstrates erythematous punctate petechial lesions on the ectocervix and purulent discharge in the vaginal vault. A vaginal swab Nucleic Acid Amplification Test (NAAT) returns positive for Trichomonas vaginalis. Which management plan follows current CDC treatment guidelines?
Oral metronidazole 500 mg twice daily for 7 days, plus partner treatment and abstinence until both finish
Oral metronidazole 2 g in a single dose, without treating her asymptomatic male sexual partner
Intravaginal metronidazole 0.75% gel once daily for 5 days, with no treatment needed for male partners
Oral azithromycin 1 g in a single dose plus clindamycin 2% vaginal cream nightly for 7 days
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