Gonorrhoea and Non-Gonococcal Urethritis
On this page
Direct answer
Gonorrhoea is a sexually transmitted infection caused by the gram-negative diplococcus Neisseria gonorrhoeae, the classic cause of purulent urethritis in men. Non-gonococcal urethritis is urethral inflammation in which gonococci are absent, and Chlamydia trachomatis is its commonest cause. The two are separated by the Gram stain of urethral discharge, which shows intracellular diplococci in gonorrhoea, and by nucleic acid amplification testing, which is the preferred modern diagnostic test.
What you must remember
- Causative organism: Neisseria gonorrhoeae is a gram-negative diplococcus found inside polymorphonuclear neutrophils on Gram stain of urethral pus.
- Gram stain rule: intracellular gram-negative diplococci on a urethral smear from a symptomatic man are diagnostic of gonorrhoea.
- NGU causes: Chlamydia trachomatis is the commonest, with Ureaplasma urealyticum, Mycoplasma genitalium, Trichomonas vaginalis and herpes simplex virus as other recognised causes.
- Incubation: gonococcal urethritis typically appears within a few days of exposure, whereas chlamydial urethritis usually takes one to three weeks.
- Gonococcal regimen: a single intramuscular dose of ceftriaxone is the recommended treatment (CDC 2021: 500 mg), with azithromycin monotherapy avoided because resistance has been reported; the NACO syndromic kit for urethral discharge instead pairs cefixime 400 mg with azithromycin 1 g.
- NGU regimen: doxycycline 100 mg twice daily for 7 days is the first-line therapy, with a single dose of azithromycin 1 g as the alternative.
- Disseminated disease: gonococci can cause a skin and joint syndrome with pustules on the distal limbs, tenosynovitis and polyarthritis.
Gonococcal versus non-gonococcal urethritis
Urethritis in men is sorted first by the Gram stain of urethral discharge, which divides the disease into a gonococcal and a non-gonococcal group with clearly different clinical pictures and treatment needs. The table compares the two groups in the way examiners test them, so each row maps to a likely exam question.
| Feature | Gonococcal urethritis | Non-gonococcal (chlamydial) urethritis |
|---|---|---|
| Organism | Neisseria gonorrhoeae | Chlamydia trachomatis, most often |
| Discharge | Profuse, thick and purulent, often with dysuria | Scanty, mucoid or mild, with less dysuria |
| Incubation | A few days | One to three weeks |
| Gram stain | Intracellular gram-negative diplococci | No gonococci, neutrophils present |
| Diagnosis | Nucleic acid amplification or culture on selective medium | Nucleic acid amplification on urine or swab |
| Regimen | Ceftriaxone intramuscular, plus cover for chlamydia | Doxycycline 100 mg twice daily for 7 days |
The table shows why the Gram stain is the decisive first test in a symptomatic man. Gonococcal and chlamydial infections frequently coexist, so the regimen covers both even when only one is confirmed, and partners need testing and treatment as well.
Where the exam plants its traps
Stems on this topic turn on the Gram stain result, the organism responsible for a discharge, and the correct single-dose regimen.
- Trap: reading a negative Gram stain as proof of chlamydia Correct: a negative Gram stain only excludes gonococci, and NAAT is needed to identify Chlamydia trachomatis.
- Trap: choosing azithromycin alone for a confirmed gonorrhoea Correct: ceftriaxone is the drug of choice for gonorrhoea, because azithromycin monotherapy has been associated with resistance.
- Trap: labelling every urethral discharge as gonorrhoea Correct: a mild, mucoid discharge with a longer incubation points to non-gonococcal urethritis, usually chlamydia.
Frequently asked questions
What is the Gram stain finding diagnostic of gonorrhoea in men?
Intracellular gram-negative diplococci inside polymorphonuclear neutrophils on a urethral smear are diagnostic of gonorrhoea in a symptomatic man. Gonorrhoea is confirmed by this finding in symptomatic men, and a negative smear still needs NAAT before chlamydia is excluded.
What is the commonest cause of non-gonococcal urethritis?
Chlamydia trachomatis is the commonest cause of non-gonococcal urethritis in men. Other recognised causes include Ureaplasma urealyticum, Mycoplasma genitalium and Trichomonas vaginalis, and the diagnosis is made by nucleic acid amplification testing.
What is the recommended regimen for gonorrhoea?
Ceftriaxone given as a single intramuscular dose is the recommended treatment for gonorrhoea under current guidance. Because chlamydia often coexists, a regimen covering it is usually added unless chlamydia has been excluded.
What is the first-line regimen for non-gonococcal urethritis?
Doxycycline 100 mg twice daily for 7 days is the first-line regimen for non-gonococcal urethritis caused by chlamydia. A single dose of azithromycin 1 g is the alternative when doxycycline cannot be used or adherence is a concern.
What skin and joint syndrome can gonococci cause?
Disseminated gonococcal infection produces a skin and joint syndrome with tenosynovitis, polyarthritis and small pustules on the distal limbs. Culture or NAAT from blood, skin lesions or joint fluid helps confirm the diagnosis, and prompt systemic treatment is required.