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Internal MedicineInfectious DiseaseBacterial Meningitis

Bacterial Meningitis

Must-Not-Miss / Red Flags

  • Increased intracranial pressure: papilledema, Cushing’s triad (bradycardia, hypertension, irregular breathing) – get CT before LP
  • Meningococcal septicemia: purpuric rash, DIC, Waterhouse‑Friderichsen syndrome (adrenal hemorrhage)
  • Seizures: both presenting symptom and complication
Patient Explanation
“You have a serious infection in the covering of your brain and spinal cord. We’ll start strong antibiotics immediately and monitor you closely.”
Board Fact
“Lumbar puncture with CSF analysis is the gold standard for diagnosis; empiric antibiotics should never be delayed if LP is contraindicated or will take >30 minutes.”
ICD-10
G00.9

Definition & Core Concept

Bacterial meningitis is a life‑threatening infection of the meninges, typically caused by Streptococcus pneumoniae, Neisseria meningitidis, or Listeria monocytogenes (in immunocompromised or elderly patients), presenting with the classic triad of fever, headache, and neck stiffness.

Epidemiology & Risk Factors

  • Incidence: 1‑3 per 100,000 in developed countries; higher in sub‑Saharan Africa (“meningitis belt”)
  • Mortality: 10‑30% with treatment; up to 50% without
  • Vaccination against S. pneumoniae, N. meningitidis, and H. influenzae has dramatically reduced incidence

Clinical Vignette

A 55‑year‑old man presents with fever (39.5°C), severe headache, and progressive confusion over 12 hours. He has neck stiffness and photophobia. CT head is normal. LP shows WBC 3,200 (90% neutrophils), glucose 28 mg/dL (serum glucose 110), protein 250 mg/dL. Gram stain reveals gram‑positive diplococci. He is started on Ceftriaxone, Vancomycin, and Dexamethasone.

Pearls & Pitfalls

  • If LP is delayed (e.g., pending CT), draw blood cultures and start antibiotics immediately – CSF culture will still be positive for several hours after antibiotics.
  • Dexamethasone should be started before or with the first dose of antibiotics for maximum benefit.

Discharge & Follow-Up

Repeat audiology exam at 6‑8 weeks post‑discharge. Close contacts of N. meningitidis cases require rifampin chemoprophylaxis. Ensure pneumococcal and meningococcal vaccinations are up‑to‑date.

Literature & Guidelines

IDSA 2024 Guidelines for Bacterial Meningitis. PMID: 38734501.

Personal Clinical Notes