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Neisseria meningitidis (Meningococcus)
Related Subjects: | Pasteurella Multocida | Capnocytophaga canimorsus | Snake Bites | Dog Bites | Tetanus | Pasteurella multocida
⚠️ A non-blanching petechial rash is an ominous sign of meningococcaemia in an acutely unwell patient. Always perform the “glass test” 🥂.
📖 About
- Meningococcaemia → invasive infection with Neisseria meningitidis, causing meningitis and/or septicaemia.
- Patients with complement (C8/C9) deficiency are especially susceptible.
📊 Epidemiology
- 13+ serogroups; main ones: A, B, C, W-135, Y.
- In the UK 🇬🇧 → serogroups B & C predominate (MenB vaccine introduced in 2015, MenACWY for teenagers).
- Bimodal age peaks: infants <5 years 👶 and teenagers 15–19 years 🎓.
🏠 Source
- Carried in the nasopharynx of ~10% of asymptomatic individuals.
🔬 Characteristics
- Gram-negative, capsulated diplococcus (kidney-shaped).
- Cell wall LPS → overproduction causes DIC, petechiae, purpura.
- Ferments glucose + maltose.
🧬 Virulence Factors
- Polysaccharide capsule → blocks phagocytosis.
- Endotoxin (LPS blebbing) → cytokine storm, septic shock.
- Pili + IgA protease → adhesion and immune evasion.
- Very rapid doubling time → sudden clinical deterioration possible.
🩺 Clinical Manifestations
- Meningitis ± septicaemia (classic presentation).
- Septicaemia alone → fever, shock, rash.
- Complications:
- Waterhouse-Friderichsen syndrome (adrenal haemorrhage 🧾).
- DIC, multiorgan failure.
- ARDS, purpura fulminans.
🔎 Investigations
- CSF Gram stain → Gram-negative diplococci inside PMNs.
- PCR for rapid confirmation (blood or CSF).
- Culture on chocolate agar or Thayer–Martin media (requires CO₂).
- Oxidase positive; ferments glucose + maltose.
💊 Antibiotic Sensitivities
- Penicillin
- Cefotaxime
- Ceftriaxone
- Rifampicin (for prophylaxis)
- Ciprofloxacin (alternative prophylaxis)
🩺 Management
- Pre-hospital: Suspected meningococcaemia with rash → give IM/IV benzylpenicillin immediately 🚑.
- Hospital therapy:
- Ceftriaxone 2 g IV BD OR Cefotaxime 2 g IV q6h.
- Penicillin (2.4 g IV q4h) if sensitive strain confirmed.
- Supportive: Aggressive fluids, vasopressors, ICU support for shock/DIC.
- Adrenal crisis: Give hydrocortisone if Waterhouse-Friderichsen suspected.
- Prophylaxis for contacts: Rifampicin, ciprofloxacin, or ceftriaxone (per UKHSA guidance).
- Vaccination: MenB (infants) + MenACWY (teenagers and at-risk groups).
💡 Exam pearl: Meningococcal rash = non-blanching petechiae/purpura. Immediate benzylpenicillin pre-hospital. In hospital: Ceftriaxone is first line.
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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