Also known as: trichomoniasis, trich, Trichomonas vaginalis, TV
Overview
Sexually transmitted infection caused by the flagellated protozoan Trichomonas vaginalis, producing vulvovaginitis in women and urethritis (often asymptomatic) in men.
Epidemiology
Most common nonviral STI globally; ~2 million US cases/year. Disproportionate prevalence in Black women (~10%) and incarcerated populations. Frequently coexists with other STIs.
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Question 1ReproductiveMedium
A 26-year-old woman presents with 5 days of frothy, malodorous yellow-green vaginal discharge, vulvar itching, and burning with urination. She is not pregnant and has had two new partners in the past 2 months. On speculum exam there is vaginal erythema and punctate cervical hemorrhages. Vaginal pH is 5.5, and saline wet mount shows motile, pear-shaped flagellated organisms. Which of the following is the most appropriate initial management?
AMetronidazole 250 mg orally three times daily for 7 days
BMetronidazole 500 mg orally twice daily for 7 days
CMetronidazole 2 g orally as a single one-time dose
DMetronidazole 0.75% vaginal gel nightly for 5 days
Reveal answer & full explanation
Correct answer: B — Metronidazole 500 mg orally twice daily for 7 days
AMetronidazole 250 mg orally three times daily for 7 days
BMetronidazole 500 mg orally twice daily for 7 days✓
CMetronidazole 2 g orally as a single one-time dose
DMetronidazole 0.75% vaginal gel nightly for 5 days
Why Metronidazole 500 mg orally twice daily for 7 days is correct
The frothy yellow-green discharge, strawberry cervix (punctate hemorrhages), pH >4.5, and motile flagellated trichomonads on wet mount confirm Trichomonas vaginalis vaginitis.
Per CDC 2021 STI treatment guidelines, first-line therapy for women is metronidazole 500 mg PO BID for 7 days; this multidose regimen replaced the single 2 g dose in women because the 7-day course produces lower recurrence.
Sexual partners should also be treated, and the patient should be re-tested within 3 months given high reinfection rates.
Why the others are wrong
Metronidazole 2 g orally as a single one-time dose — correct drug class, but the single dose is now first-line only for men; in women it has higher recurrence and is no longer preferred.
Metronidazole 250 mg orally three times daily for 7 days — a superseded lower-dose oral regimen that delivers less total drug than the currently recommended course; CDC specifies 500 mg twice daily for 7 days in women.
Metronidazole 0.75% vaginal gel nightly for 5 days — topical metronidazole treats bacterial vaginosis but does not reach therapeutic levels in the urethra and periurethral glands where trichomonads persist, so cure rates are poor and it is explicitly not recommended for trichomoniasis.
Question 2ReproductiveMedium
A 25-year-old woman at 26 weeks' gestation reports a 1-week history of frothy, malodorous yellow-green vaginal discharge with vulvar burning. On speculum exam, the cervix shows punctate hemorrhages and vaginal pH is 5.5. A nucleic acid amplification test confirms Trichomonas vaginalis, and she begins metronidazole 500 mg PO twice daily for 7 days. Which of the following complications is this infection most likely to contribute to in this patient?
ANeonatal sepsis
BPreterm delivery
CPostpartum hemorrhage
DPlacental abruption
Reveal answer & full explanation
Correct answer: B — Preterm delivery
ANeonatal sepsis
BPreterm delivery✓
CPostpartum hemorrhage
DPlacental abruption
Why Preterm delivery is correct
Trichomoniasis in pregnancy is associated with adverse obstetric outcomes — preterm birth, premature rupture of membranes, and low birth weight — driven by ascending genital inflammation.
In a confirmed, symptomatic pregnant patient, preterm delivery is the highest-yield trichomoniasis-related complication to recognize; the CDC recommends treating symptomatic infection in pregnancy.
Note that while symptomatic infection is treated, antibiotic therapy does not consistently reduce the preterm birth risk, so it remains the key associated outcome.
Why the others are wrong
Placental abruption — abruption is driven by chronic or gestational hypertension, trauma, cocaine use, and smoking; T. vaginalis is not a recognized cause, and she has no bleeding, uterine tenderness, or elevated blood pressure.
Neonatal sepsis — early-onset neonatal sepsis follows group B streptococcal or coliform colonization with chorioamnionitis; Trichomonas is a lower-tract protozoal infection and is not an established cause of invasive neonatal infection.
Postpartum hemorrhage — bleeding after delivery reflects uterine atony, retained placental tissue, genital tract laceration, or coagulopathy, none of which trichomoniasis produces.
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Lower socioeconomic status / limited healthcare access
Pathophysiology
T. vaginalis adheres to vaginal epithelium via surface adhesins and produces cytotoxins, causing epithelial inflammation, micro-ulceration, and increased risk of HIV transmission/acquisition. The organism cannot survive outside the urogenital tract.
Clinical presentation
Symptoms
Frothy, malodorous yellow-green discharge
Vulvar and vaginal pruritus, burning
Dyspareunia, dysuria
Postcoital bleeding
~50% of women and most men are asymptomatic
Signs / physical exam
Frothy yellow-green discharge
Vulvovaginal erythema
'Strawberry cervix' (punctate hemorrhages) — pathognomonic but seen in only ~2-5%
Vaginal pH >4.5
Classic findings
Sexually active woman with frothy malodorous discharge, vulvar pruritus, and strawberry cervix on colposcopy or speculum exam.
Women: metronidazole 500 mg PO BID × 7 days (CDC 2021 — replaced single 2 g dose for women based on trial data showing lower recurrence with 7-day regimen)
Men: metronidazole 2 g PO × 1 dose
Alternative: tinidazole 2 g PO × 1 dose
Pregnancy
Treat symptomatic infection — metronidazole 500 mg PO BID × 7 days (or 2 g × 1 dose)
Metronidazole crosses placenta but evidence does not support teratogenicity; benefits outweigh risks
Avoid tinidazole in pregnancy
Counsel about preterm birth risk; treatment does not consistently reduce this risk
HIV-positive women
Metronidazole 500 mg PO BID × 7 days (single-dose regimen less effective)
Re-screen at 3 months
Important to treat — increases viral shedding and transmission
Second-line / adjunct
Treatment failure: re-treat with metronidazole 500 mg PO BID × 7 days; if persistent, tinidazole 2 g PO daily × 7 days; if still refractory, susceptibility testing and high-dose tinidazole
Avoid alcohol during and for 24 hours after metronidazole (72 hours after tinidazole) — disulfiram-like reaction
All current sexual partners should be treated regardless of symptoms (expedited partner therapy where legal)
Re-test all women within 3 months due to high reinfection rate
Complications
Increased risk of HIV transmission and acquisition
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