Microbiology · MU Sofia

52. Neisseria gonorrhoeae

Covers the morphology and growth requirements of Neisseria gonorrhoeae, then its virulence factors such as pili, porins, Opa proteins and lipooligosaccharide, followed by transmission and the clinical forms of gonorrhoea, disseminated infection and ophthalmia neonatorum. Diagnostic methods, treatment regimens and prevention come next, with a table contrasting the species with N. meningitidis and a closing summary. Tables set out the virulence factors, diagnostic methods and species comparison.

Inside: 10 sections · 6 labelled pictures · 3 tables · 15 flashcards · 4 min

Topic 52 of 113 in the MU Sofia syllabus for Microbiology (Medicine, Year 3). The free AceMed note covers it in 10 sections, about 357 words (4 min of reading), with 15 flashcards.

In this note

  1. Neisseria gonorrhoeae (Gonococcus)
  2. I. General Characteristics
  3. II. Virulence Factors and Mechanism of Pathogenesis
  4. III. Transmission & Epidemiology
  5. IV. Diseases Caused by N. gonorrhoeae
  6. V. Diagnosis
  7. VI. Treatment
  8. VII. Prevention
  9. VIII. Differences: N. gonorrhoeae vs. N. meningitidis
  10. IX. Summary Points

I. General Characteristics

  • Gram-negative, kidney-shaped diplococci, often seen intracellularly within neutrophils.
  • Unencapsulated (unlike N. meningitidis).
  • Obligate human pathogen – not found in animals or in healthy carriers.
  • Non-motile, non-spore forming, aerobic.
  • Fastidious – requires enriched media:
  • Chocolate agar
  • Thayer-Martin agar (selective for Neisseria – contains antibiotics).
  • Growth requires 5–10% CO₂.
  • Oxidase positive (produces purple color).
  • Ferments glucose only (distinguishes it from N. meningitidis, which also ferments maltose).
  • Sensitive to drying and cold – must be transported immediately.

II. Virulence Factors and Mechanism of Pathogenesis

Antigenic variation in pili and outer membrane proteins → repeated infections possible, no long-term immunity.

III. Transmission & Epidemiology

  • Sexual contact – most common mode.
  • Vertical transmission – from mother to neonate during childbirth → ophthalmia neonatorum.
  • Risk factors:
  • Multiple sexual partners.
  • Unprotected intercourse.
  • Sexually active adolescents and young adults.
  • Not found in healthy carriers unlike N. meningitidis.

IV. Diseases Caused by N. gonorrhoeae

1. Gonorrhoea (STI)

  • Incubation: 2–5 days.
  • Males:
  • Urethritis → dysuria, purulent yellow/white discharge, painful urination.
  • Can lead to prostatitis, epididymitis.
  • Females:
  • Often asymptomatic (up to 60%).
  • Cervicitis → vaginal discharge, pelvic pain, bleeding.
  • Can progress to PID (Pelvic Inflammatory Disease) → infertility, ectopic pregnancy.
  • Rectal gonorrhoea – anal pain, discharge.
  • Pharyngeal gonorrhoea – often asymptomatic.

2. Disseminated Gonococcal Infection (DGI)

  • Gonococci spread via blood to other sites.
  • Symptoms:
  • Fever, pustular rash with erythematous base.
  • Septic arthritis, especially in knees/wrists.
  • Tenosynovitis.

3. Ophthalmia Neonatorum

  • Purulent conjunctivitis in neonates.
  • Acquired during vaginal delivery.
  • Can cause blindness if not treated early.

4. Other Sites

  • Endocarditis, meningitis (rare).
  • Bartholinitis in females, proctitis in MSM.

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