Types of Vaginal Infections
The three most common vaginal infections are bacterial vaginosis (BV), vulvovaginal candidiasis (yeast infection), and trichomoniasis, which together account for over 90% of all cases of infectious vaginitis. 1, 2
The Three Primary Vaginal Infections
Bacterial Vaginosis (BV)
BV is the most prevalent cause of vaginal discharge or malodor, resulting from replacement of normal H₂O₂-producing Lactobacillus species with an overgrowth of anaerobic bacteria including Gardnerella vaginalis, Prevotella species, Mobiluncus species, and Mycoplasma hominis. 1, 3
Clinical Presentation
- Homogeneous, thin white discharge that smoothly coats the vaginal walls (not frothy or green) 1, 4
- Fishy odor, particularly after intercourse or with alkaline exposure 1, 4
- Vaginal pH greater than 4.5 (normal is 3.8-4.2) 1, 5
- Notably lacks significant vulvar inflammation or itching 1, 4
- Up to 50% of women meeting diagnostic criteria are completely asymptomatic 3
Diagnosis
BV requires three of four Amsel criteria: 1
- Homogeneous, white, noninflammatory discharge
- Clue cells on microscopic examination (>20% of epithelial cells with bacteria attached to borders) 1, 2
- Vaginal pH >4.5
- Positive whiff test (fishy odor with 10% KOH application) 1, 5
Alternatively, Gram stain showing loss of lactobacilli and predominance of mixed anaerobic morphotypes (Nugent score ≥4) confirms the diagnosis. 1, 6
Treatment
- Metronidazole (oral or intravaginal) is first-line therapy 7, 8
- Tinidazole 2g once daily for 2 days OR 1g once daily for 5 days are FDA-approved alternatives 6
- Treating male partners does NOT prevent recurrence, as BV represents dysbiosis rather than simple sexual transmission 1, 3
- Treatment is indicated for all symptomatic women regardless of pregnancy status 1
Important Clinical Considerations
BV significantly increases risk for serious complications including: 3
- Pelvic inflammatory disease (PID), endometritis, and vaginal cuff cellulitis after invasive procedures
- Preterm labor, premature rupture of membranes, and postpartum endometritis in pregnancy
- Post-abortion infections and post-cesarean infections
Consider treating asymptomatic BV before surgical abortion or other invasive gynecologic procedures to prevent ascending infections. 3
Vulvovaginal Candidiasis (Yeast Infection)
Candidiasis is typically caused by Candida albicans, though C. tropicalis and C. glabrata are increasingly prevalent, with approximately 15% of C. albicans strains resistant to clotrimazole and miconazole. 2
Clinical Presentation
- Thick, white "curdled" or cottage cheese-like discharge 2
- Intense vulvar pruritus (itching) as the predominant symptom 2
- Hyperemic (red) vagina with erythematous and/or excoriated vulva 2
- Normal vaginal pH (3.8-4.2) in uncomplicated cases 2
- External vulvar inflammation is prominent 1
Diagnosis
- Microscopic examination reveals budding yeast or pseudohyphae in 50-70% of cases 2, 9
- KOH preparation enhances visualization of yeast forms 1
- Culture may be required when microscopy is negative but clinical suspicion remains high 8, 10
Treatment
- Intravaginal imidazoles (clotrimazole, miconazole) are recommended initial therapy 8, 10
- Oral fluconazole is an effective alternative 10
- Recurrent infections (≥4 episodes per year) may require fluconazole 150mg weekly for up to 12 consecutive weeks 2
- Partner treatment is NOT necessary unless the partner is symptomatic 11
- Only symptomatic infections require treatment 11
Trichomoniasis
Trichomoniasis is a sexually transmitted protozoal infection caused by Trichomonas vaginalis, characterized by a frothy greenish discharge with prominent itching. 4, 6
Clinical Presentation
- Frothy, greenish discharge (pathognomonic feature) 4
- Foul odor 2
- Prominent vulvar itching and irritation 4
- Vaginal pH >4.5 (present in 70% of cases) 2
- Punctate cervical microhemorrhages ("strawberry cervix") in 25% of cases 2
Diagnosis
- Wet mount showing motile trichomonads detects 50-75% of cases 2, 9
- Culture is more sensitive than microscopic examination and should be used when wet mount is negative but clinical suspicion is high 1, 8
- Fluorescent monoclonal antibodies increase microscopic detection sensitivity 9
Treatment
- Metronidazole 2g single oral dose is the recommended treatment 7, 2
- Tinidazole 2g single oral dose is an FDA-approved alternative 6
- Sexual partners MUST be treated simultaneously to prevent reinfection, as treatment failure is usually due to untreated partners 4, 6, 8
- Screen for other STIs (chlamydia, gonorrhea) as trichomoniasis is sexually transmitted 4
Other Causes of Vaginal Discharge
Mucopurulent Cervicitis (MPC)
Cervicitis caused by Chlamydia trachomatis or Neisseria gonorrhoeae can sometimes present with vaginal discharge. 1, 11 These pathogens should be ruled out when evaluating vaginal symptoms, particularly in sexually active women. 6
Non-Infectious Causes
Mechanical, chemical, or allergic irritation can present with vulvar inflammation and minimal discharge in the absence of vaginal pathogens. 1, 5
Common irritants include: 5
- Regular soap (use only water or mild soap for external cleansing)
- Douches and vaginal products
- Chemical irritants that disrupt the protective vaginal ecosystem
Critical Diagnostic Approach
A pelvic examination with office laboratory testing is essential for accurate diagnosis, as symptoms and physical examination alone are inadequate. 11, 10
Essential Office Tests
- Vaginal pH testing (normal 3.8-4.2; elevated >4.5 suggests BV or trichomoniasis) 1, 5
- Wet mount examination in normal saline (for trichomonads, clue cells) 1
- KOH preparation (for yeast, positive whiff test) 1
- Microscopic examination at low and high-dry power 1
Common Pitfall
More than one infection can coexist simultaneously—appropriate tests for all three common agents should be performed during vaginal examination. 9 Laboratory testing fails to identify the cause in a substantial minority of women, and culture or nucleic acid testing may be required. 1, 10