A 28-year-old man presents with purulent urethral discharge and dysuria for 3 days. Gram stain of urethral smear shows intracellular gram-negative diplococci. Which single feature best distinguishes Neisseria gonorrhoeae infection from Chlamydia trachomatis urethritis in this patient?

## Discriminating Features: Gonorrhea vs. Chlamydia ### Gram Stain Morphology **Key Point:** Neisseria gonorrhoeae appears as **intracellular gram-negative diplococci** (kidney bean–shaped) within polymorphonuclear leukocytes on Gram stain of urethral smear. This is the gold standard for presumptive diagnosis of gonorrhea in men. **High-Yield:** Chlamydia trachomatis is an obligate intracellular bacterium that does NOT stain with Gram stain — it requires special stains (Giemsa, immunofluorescence) or nucleic acid amplification tests (NAAT). The absence of organisms on Gram stain in a symptomatic patient strongly suggests chlamydia. ### Comparison Table | Feature | Gonorrhea | Chlamydia | | --- | --- | --- | | **Gram stain appearance** | Intracellular gram-negative diplococci | Not visible on Gram stain | | **Incubation period** | 2–5 days (acute) | 7–14 days (often longer) | | **Urethral discharge** | Purulent, copious | Mucopurulent or scant | | **Culture** | Grows on Thayer-Martin medium | Cannot be cultured routinely; requires cell culture or NAAT | | **Asymptomatic carriage** | ~5–10% in men | ~25–50% in men; ~50% in women | ### Clinical Pearl In men with acute urethritis and Gram stain–positive intracellular gram-negative diplococci, gonorrhea is presumed and treatment initiated immediately. Absence of organisms on Gram stain does not exclude gonorrhea but raises suspicion for chlamydia or other organisms. ### Mnemonic **GC-GN-ID:** **G**onorrhea = **G**ram-negative, **I**ntracellular **D**iplococci (kidney bean shape).