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Infectious Disease

Bacterial Meningitis

Life-threatening bacterial infection of the meninges presenting with fever, headache, neck stiffness and altered mental status. Do not delay empiric antibiotics and dexamethasone.

Last reviewed 26 Jun 2026 - MedicoMedics editorial team

Bacterial meningitis with purulent meningeal inflammation

Pathophysiology

Adults <50: Streptococcus pneumoniae, Neisseria meningitidis. Neonates: GBS, E. coli, Listeria. >50 or immunocompromised: add Listeria.

Sources: IDSA Meningitis (Clin Infect Dis 2004;39:1267); Dexamethasone (NEJM 2002;347:1549)

Presentation

Fever, neck stiffness, altered mental status (all three in ~44%). Meningococcaemia: petechial rash. Kernig, Brudzinski insensitive.

Diagnosis

LP after CT if focal deficit, seizure, immunocompromise. CSF: neutrophilic pleocytosis, glucose <40% serum, high protein, positive Gram stain and culture.

Management

Do NOT delay antibiotics for imaging. Empiric <50: ceftriaxone + vancomycin. >50 or immunocompromised: add ampicillin. Dexamethasone 10 mg IV q6h with first dose reduces mortality in pneumococcal.

Sample USMLE-style MCQs

Try 5 questions on this topic. Practice hundreds more free with a trial.

Question 1

24-year-old fever, headache, petechial rash. CSF: 3200 neutrophils, glucose 20, Gram-negative diplococci. Contact prophylaxis?

Question 2

68-year-old suspected meningitis, empiric regimen?

Question 3

Classic CSF pattern in bacterial meningitis?

Question 4

Who requires CT before LP?

Question 5

Vaccine reducing invasive pneumococcal disease in adults >=65?

References

Primary guidelines and peer-reviewed sources used for this entry. Reviewed 26 Jun 2026 by MedicoMedics editorial team.

  1. IDSA Meningitis (Clin Infect Dis 2004;39:1267)
  2. Dexamethasone (NEJM 2002;347:1549)

Frequently asked

Adjunct improving outcome?

Dexamethasone with first antibiotic dose.

When CT before LP?

Immunocompromise, focal deficit, seizure, papilloedema, GCS <=10.

Meningococcal prophylaxis?

Single-dose ciprofloxacin or rifampin BID x 2 days.

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