Organism: Trichomonas vaginalis

Type: Protozoan parasite (flagellated)

Disease: Trichomoniasis – a sexually transmitted vaginitis.

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1. Protozoan with 4 anterior flagella + undulating membrane.
2. Causes frothy yellow-green discharge, fishy smell, strawberry cervix.
3. pH > 4.5 (alkaline).
4. Motile trophozoites seen on wet mount (gold standard in resource settings).
5. No cyst form → dies quickly outside body → transmission only via sex.
6. Symptoms more severe during menstruation (pH rises).
7. Treatment: Both partners must be treated → Metronidazole or Tinidazole.
8. Associated with ↑ risk of HIV infection, preterm delivery, PID.
9. Often coexists with other STIs.
10. Men: usually asymptomatic carriers (urethritis).

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🔬 FULL MICROBIOLOGY — CLEAR & COMPLETE

1️⃣ Organism Basics

• Trichomonas vaginalis is a protozoan parasite.
• Shape: Pear-shaped.
• Movement: Rapid, jerky, “tumbling” due to flagella.
• Structure:
• 4 anterior flagella
• 1 posterior flagellum
• Undulating membrane (high-yield exam point).

❌ No cyst form

• Only exists as a trophozoite.
• Dies quickly in environment → requires direct mucosal contact → sexual transmission.

📌 Memory: “Trichomonas has Trich → Tricky undulating membrane + flagella.”

2️⃣ Epidemiology

• Most common non-viral STI worldwide.
• Higher prevalence in women.
• Men = reservoirs, often asymptomatic.
• Spread by sexual contact only (no cyst → no fomites).
• Incubation: 4–28 days.

3️⃣ Pathogenesis — How it Causes Disease

1. Parasite adheres to vaginal/urethral epithelium.
2. Produces proteases that destroy epithelial cells.
3. Causes inflammation → ↑ discharge.
4. Increases vaginal pH (organism likes alkaline environment).
5. Capable of phagocytosis → eats bacteria + host cells.

4️⃣ Clinical Features

A. In Women

Classic triad:

1. Frothy yellow-green discharge
2. Fishy odor
3. Strawberry cervix (petechiae on cervix) – high-yield

Other symptoms:

• Itching
• Dysuria
• Dyspareunia
• Vaginal soreness
• Vulval irritation
• pH > 4.5

Symptoms worse during menstruation due to alkaline blood.

B. In Men

Mostly asymptomatic, but may cause:

• Urethritis
• Epididymitis
• Prostatitis
• Thin discharge
• Dysuria

Men = common carriers, easily re-infect partners.

5️⃣ Diagnosis – HIGH-YIELD

✔ 1. Wet mount microscopy

• Shows motile trophozoites
• Sensitivity ~60%
• Must examine sample immediately

✔ 2. pH > 4.5

• BV and Trichomonas both have alkaline pH
• Candida has normal pH

✔ 3. NAAT / PCR (BEST modern test)

• Highest sensitivity
• Detects parasite DNA
• Recommended in all high-resource settings

✔ 4. Culture

• Diamond’s medium → highly sensitive
• Used when NAAT unavailable

✔ 5. Whiff test

• Can also be positive (fishy smell)
• But less specific than BV

6️⃣ Treatment – VERY IMPORTANT

⭐ FIRST-LINE

• Metronidazole 2 g single dose

OR

• Metronidazole 500 mg BID × 7 days

OR

• Tinidazole 2 g single dose

⭐ MUST TREAT BOTH PARTNERS

• Prevent reinfection
• Abstain from sex until both partners complete treatment and symptoms resolve

⭐ Pregnancy

• Metronidazole is safe
• Treat symptomatic pregnant women

⭐ Breastfeeding

• Avoid breastfeeding for 12–24 hours after metronidazole 2 g dose
• Or use 7-day regimen instead

7️⃣ Complications

• Increased risk of HIV acquisition
• Preterm delivery
• Low birth weight
• Premature rupture of membranes
• PID (especially with co-infections)
• Cervical neoplasia risk increases

8️⃣ Differentiation Table

TRICHOMONAS VAGINALIS — COMPLETE MASTER TABLE (ZERO OMISSION)