Gonorrhea (Neisseria gonorrhoeae)
The causative organism is Neisseria gonorrhoeae—the finding of gram-negative intracellular diplococci on Gram stain of urethral discharge in a symptomatic male is diagnostic for gonococcal urethritis with >99% specificity and >95% sensitivity. 1
Why This is Gonorrhea
- The Centers for Disease Control and Prevention defines gonorrhea by the observation of gram-negative intracellular diplococci in a urethral smear obtained from a male as a laboratory criterion for diagnosis 2
- This Gram stain finding in symptomatic men with urethral discharge is diagnostic for gonorrhea without requiring culture confirmation 1
- The probability of gonorrhea in men with urethral discharge whose smears contain intracellular gram-negative diplococci is 94.8% 3
Why Not the Other Organisms
- Chlamydia trachomatis: Cannot be visualized on Gram stain—it is an obligate intracellular bacterium that requires nucleic acid amplification tests or culture for diagnosis 1
- Mycoplasma genitalium: Lacks a cell wall and cannot be seen on Gram stain; requires specialized molecular testing 1
- Ureaplasma urealyticum: Also lacks a cell wall and is not visible on Gram stain; requires specialized culture or molecular methods 1
Critical Diagnostic Pitfall to Avoid
- Neisseria meningitidis can also appear as gram-negative intracellular diplococci on urethral Gram stain and has been associated with urethritis in men who receive oral sex, as it colonizes the nasopharynx 4
- However, N. gonorrhoeae remains by far the most common cause of this clinical presentation, and empiric treatment should target gonorrhea 2, 1
- Branhamella (Moraxella) catarrhalis can rarely cause urethritis with similar Gram stain appearance, but this is exceedingly uncommon 5
Immediate Next Steps
- Treat empirically for both gonorrhea AND chlamydia immediately, as coinfection is common and dual therapy is recommended 1, 6
- Send nucleic acid amplification tests for both N. gonorrhoeae and C. trachomatis on first-void urine or urethral swab for confirmation 1, 6
- Perform comprehensive STI screening including syphilis serology and HIV testing 1
- Instruct the patient to refer sex partners from the preceding 60 days for evaluation and presumptive treatment 1