Microbiology · Gram-negative cocci
Neisseria gonorrhoeae !
- Bacterium
- Gram-negative
- Exam priority: high
A sexually transmitted bacterium that causes gonorrhea; in women it often gives no symptoms and can lead to infertility.
Updated 2026-11-01
Also called: gonococcus
At a glance
- Gram
- Gram-negative
- Shape
- Coffee-bean diplococcus
- Oxygen
- Aerobic
- Family
- Neisseriaceae
- Stain
- Gram: red diplococci inside neutrophils in urethral discharge
Morphology
- Gram-negative diplococci with no capsule
- Oxidase-positive; ferments glucose only
- Needs enriched media: chocolate agar or Thayer-Martin, in CO2
Transmission
- Vaginal, oral or anal sex
- Mother to newborn during birth (neonatal conjunctivitis)
- Repeat infections: no protective immunity
Reservoir: Humans only
Isolation precautions
What the care team adds to standard precautions.
- Standard
Virulence factors
- Pili with antigenic variation: mucosal attachment and antibody escape
- Opa and Por proteins: attachment, invasion and blocking of phagocytosis
- Lipooligosaccharide (LOS): local inflammation
- IgA protease
- Readily picks up resistance genes
Diseases it causes
- Urethritis with pus in men; cervicitis, often silent, in women Gonorrhoea →
- Pelvic inflammatory disease, ectopic pregnancy and infertility Pelvic inflammatory disease →
- Disseminated gonococcal infection with septic arthritis (knee, wrist), tenosynovitis and skin pustules Septic Arthritis of the Knee →
- Epididymitis in men Epididymitis →
- Purulent conjunctivitis of the newborn (ophthalmia neonatorum), which can cause blindness Conjunctivitis →
Clinical picture
- Dysuria and thick urethral discharge a few days after exposure
- Pharyngitis and proctitis depending on sexual practice
- Perihepatitis (Fitz-Hugh-Curtis syndrome) as a complication of pelvic inflammatory disease
Diagnosis
- Nucleic acid amplification tests (NAAT) on urine or swabs: test of choice
- Gram stain of male urethral discharge: intracellular Gram-negative diplococci
- Culture on Thayer-Martin to test antibiotic susceptibility
- Test also for Chlamydia, HIV and syphilis
Treatment
Third-generation cephalosporins: intramuscular ceftriaxone is preferred; oral cefixime only when that is not possible. Chlamydia co-infection and sex partners are treated too. Resistance keeps rising: penicillins, tetracyclines and quinolones no longer work in many regions.
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
Prevention
- Condoms every time
- Screening of people at risk and treatment of partners
- Eye prophylaxis for newborns
- No vaccine
Test yourself
Think of the answer, then tap the question to see it.
Which Gram stain finding in urethral discharge suggests gonorrhea in a man?
Gram-negative diplococci inside neutrophils.
Why can a person get gonorrhea again and again?
Its pili change antigen and it has no capsule, so infection leaves no protective immunity.
Which triad suggests disseminated gonococcal infection?
Arthritis (often knee or wrist), tenosynovitis and pustular skin lesions.
Which antibiotic class is the basis of current treatment?
Third-generation cephalosporins, with ceftriaxone as the drug of choice.
Related
Related conditions
← Back to the group: Gram-negative cocci
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Gonorrhoea (Neisseria gonorrhoeae infection) (WHO, 2025); Antimicrobial resistance (WHO, 2026).
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Representative model, for educational purposes only.