Bacterial meningitis (age over 1 month)
Acute purulent infection of the meninges beyond the neonatal period, most often from Streptococcus pneumoniae or Neisseria meningitidis, diagnosed by CSF analysis after prompt lumbar puncture and treated with immediate empiric intravenous antibiotics plus adjunctive dexamethasone, since any delay in therapy worsens outcome and mortality remains near 25%.
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What this article covers
- Overview
Acute purulent (bacterial) infection of the leptomeninges and subarachnoid space beyond the first month of life, producing the classic triad of fever, neck stiffness, and altered mental status.
- Epidemiology
Streptococcus pneumoniae is the most common cause of community-acquired bacterial meningitis, though H.
- Risk factors
Age over 50 years or impaired cell-mediated immunity: raises the risk of Listeria monocytogenes, which must be covered empirically.
- Pathophysiology
Nasopharyngeal colonization by an encapsulated organism (S.
- Clinical features
The classic triad is fever, nuchal rigidity, and altered mental status, present in most patients with acute community-acquired bacterial meningitis.
- Differential diagnosis
Viral meningitis: lymphocytic CSF pleocytosis (though up to 25% neutrophil-predominant early), glucose over 45 mg/dL (CSF-to-plasma ratio usually ≥0.40), protein under 200 mg/dL, and a negative Gram…
- Diagnosis
The diagnostic basis is the bacterial CSF profile on lumbar puncture (LP): neutrophil-predominant pleocytosis (typically 1,000-5,000/µL), glucose under 40 mg/dL, protein elevated (median 390 mg/dL)…
- Management
First, obtain blood cultures immediately, then give adjunctive dexamethasone 0.15 mg/kg IV every 6 hours, with the first dose given concomitantly with (just before or with) the first dose of…
- Complications
Death: mortality remains approximately 25% despite antibiotic therapy.
- Prognosis
Mortality is approximately 25% despite appropriate antibiotic therapy, underscoring the need for immediate empiric treatment.
- Prevention
Conjugate meningococcal vaccine (covers serogroups A, C, W, Y) is standard; because it does not include serogroup B (about 40% of US meningococcal disease), a separate serogroup B meningococcal…
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