Acute Bacterial Meningitis (Adults) ✅

Related Subjects: |Adrenal Physiology |Addisons Disease |Lumbar Puncture |CSF Interpretation

💉 Immediate Action: In suspected adult meningococcal meningitis or septicaemia, give antibiotics immediately – ideally before hospital referral. If already in hospital, administer before lumbar puncture (LP). Early therapy significantly reduces mortality.

🚑 Initial Management Summary (Adult Bacterial Meningitis)

• 🫁 ABC stabilization: Airway, breathing, circulation; monitor vitals; admit for LP. Perform CT first if signs of SOL, papilloedema, or focal deficits.
• 🧪 Take blood cultures before antibiotics if feasible; CSF culture after LP.
• 💊 Empirical therapy (UK NICE / BNF): Cefotaxime 2g QDS or Ceftriaxone 2g BD.
• ➕ Add IV Amoxicillin if Listeria suspected (age >50, pregnancy, immunocompromised).
• ➕ Add Vancomycin if penicillin-resistant pneumococcus or post-neurosurgical meningitis suspected.
• ➕ Add IV Aciclovir if viral encephalitis suspected (HSV).
• 💊 Dexamethasone 0.15 mg/kg IV (≈10 mg) every 6h for 4 days – ideally before or with first antibiotic dose.
• 🏥 Supportive care: fluids, oxygen, seizure management, monitoring for shock.

📖 Key Points

• Untreated bacterial meningitis mortality: 70–100%.
• Base treatment on clinical suspicion – do not delay for LP/CT.
• Atypical presentations common in elderly, immunocompromised, or young children.
• Early recognition and intervention drastically reduce mortality and long-term complications.

🧬 Aetiology & Pathophysiology

• Bacteria invade subarachnoid space → intense inflammation → cerebral edema, thrombophlebitis, raised ICP.
• Common organisms: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae.
• Pathogenesis: nasopharyngeal colonisation → bloodstream invasion → blood-brain barrier penetration → purulent exudate.

🦠 Common Organisms & Empirical Therapy

🧾 Clinical Presentation

• Classic triad: Fever, Neck stiffness, Altered mental status (~45% cases).
• Other features: headache, photophobia, vomiting, seizures, rash (meningococcal).
• Elderly/immunocompromised: may present subtly; meningism often absent.
• Advanced: cranial nerve palsies (VI common), papilloedema, coma.

⚠️ Complications

• Seizures, stroke, SIADH / hyponatraemia.
• Hydrocephalus, herniation, cerebral abscess.
• Septic shock, DIC (especially meningococcal).

🔎 Investigations

• Bloods: FBC, U&E, CRP, glucose, cultures.
• CT head: if reduced GCS, focal neurology, papilloedema.
• CSF (LP, after imaging if needed):
  • Bacterial: high neutrophils, ↑protein, ↓glucose ratio <0.4.
  • Viral: lymphocytes, normal glucose, mild ↑protein.
  • TB/fungal: lymphocytes, very low glucose, very high protein.

💊 Management Principles

• Give immediate antibiotics – do not wait for LP or imaging.
• Dexamethasone ideally before or with first antibiotic dose to reduce neurological complications.
• Supportive: IV fluids, oxygen, seizure control.
• Early referral to neurosurgery / ID if complications: abscess, hydrocephalus, raised ICP.

👨‍👩‍👧 Close Contact Prophylaxis

• Rifampicin 600 mg PO BD × 2 days.
• Alternatives: Ciprofloxacin 500 mg PO single dose, or Ceftriaxone 250 mg IM single dose.
• Follow local Public Health / PHE guidance.

📝 Student / Exam Tips

• ⚡ “Red flag” = sudden fever + neck stiffness + altered mental status → treat as bacterial meningitis until proven otherwise.
• 💉 Antibiotics do not wait for LP if high suspicion.
• 🧪 Blood cultures ideally before antibiotics.
• 💊 Dexamethasone reduces risk of hearing loss and neurological sequelae in pneumococcal meningitis.
• 🚨 Know common organisms by age/risk factors; Listeria in elderly/pregnant/immunocompromised.
• 🖼 Imaging (CT) is required if reduced GCS, focal neuro signs, or papilloedema.
• 👨‍👩‍👧 Close contacts need prophylaxis; important in exams to mention.

📚 References / Guidelines

• NICE CG102 – Meningitis and Meningococcal Septicaemia (2016)
• Norfolk & Norwich University Hospital – Adult Bacterial Meningitis Guideline
• CDC – Meningitis Overview
• WHO Fact Sheet – Meningitis