I. General Characteristics
- Gram-negative, kidney-shaped diplococci, often found inside neutrophils in CSF.
- Encapsulated (unlike N. gonorrhoeae) – this capsule is the most important virulence factor.
- Oxidase positive and catalase positive.
- Non-motile, non-spore forming.
- Aerobic, but grows best in 5–10% CO₂.
- Requires enriched media like chocolate agar or Thayer-Martin agar (a selective medium).
- Ferments glucose and maltose (important diagnostic feature; N. gonorrhoeae ferments only glucose).
- Reservoir: Human nasopharynx – can be carried asymptomatically.
II. Structure and Virulence Factors
Serogroup B capsule is poorly immunogenic (made of sialic acid), which is why it's harder to make a vaccine against it.
II. Transmission & Pathogenesis
- Spread via airborne respiratory droplets or close contact (e.g., in dormitories, military).
- Colonizes the nasopharyngeal mucosa → enters bloodstream (bacteremia) → crosses blood-brain barrier → meningitis.
- Can also trigger meningococcemia – a systemic, life-threatening sepsis-like illness.
- Incubation period: 1–7 days.
IV. Diseases Caused
- 1. Meningitis
- Inflammation of the meninges (brain + spinal cord coverings).
- Rapid onset: fever, headache, photophobia, neck stiffness, vomiting, and altered mental status.
- High mortality if untreated.
- 2. Meningococcemia
- Severe bacteremia with systemic symptoms.
- Signs: petechial rash → purpura → disseminated intravascular coagulation (DIC), hypotension, shock, and Waterhouse-Friderichsen syndrome (adrenal gland hemorrhage).
- May occur with or without meningitis.