What are the empiric antibiotic regimens for meningitis?

Empiric Antibiotic Regimens for Meningitis

For suspected bacterial meningitis, all patients should receive ceftriaxone 2g IV every 12 hours or cefotaxime 2g IV every 4-6 hours as the cornerstone of empiric therapy, with additional agents based on age and risk factors. 1

Age-Based Empiric Regimens

Neonates (<1 month)

• First-line: Ampicillin/amoxicillin 50 mg/kg IV every 8 hours PLUS cefotaxime 50 mg/kg IV every 8 hours 1, 2
• Alternative: Ampicillin/amoxicillin PLUS aminoglycoside 2

Children (1 month to 18 years)

• First-line: Ceftriaxone 50 mg/kg (max 2g) every 12 hours OR cefotaxime 75 mg/kg every 6-8 hours 1, 2
• Add vancomycin 10-15 mg/kg every 6 hours if pneumococcal meningitis cannot be ruled out or in areas with high pneumococcal resistance 1, 3

Adults (18-50 years) without risk factors for Listeria

• First-line: Ceftriaxone 2g IV every 12 hours OR cefotaxime 2g IV every 4-6 hours 1, 2
• Add vancomycin 15-20 mg/kg IV every 8-12 hours OR rifampicin 600 mg every 12 hours if penicillin-resistant pneumococci is suspected (e.g., recent travel to areas with high resistance) 1

Adults >50 years OR immunocompromised patients

• First-line: Ceftriaxone 2g IV every 12 hours OR cefotaxime 2g IV every 4-6 hours 1, 2
• PLUS ampicillin/amoxicillin 2g IV every 4 hours (for Listeria coverage) 1, 2
• PLUS vancomycin 15-20 mg/kg IV every 8-12 hours OR rifampicin 600 mg every 12 hours if penicillin-resistant pneumococci is suspected 1

Special Considerations

Beta-lactam allergy

• Severe allergy: Chloramphenicol 25 mg/kg IV every 6 hours 1, 2

Adjunctive therapy

• Dexamethasone 10 mg IV every 6 hours for 4 days, starting before or with the first antibiotic dose 2
• Consider discontinuing if the causative organism is neither H. influenzae nor S. pneumoniae 2

Pathogen-Specific Therapy (After Identification)

Streptococcus pneumoniae

• Penicillin-sensitive (MIC ≤0.06 mg/L): Continue ceftriaxone/cefotaxime OR switch to benzylpenicillin 2.4g IV every 4 hours; treat for 10 days if recovered, 14 days if not 1
• Penicillin-resistant but cephalosporin-sensitive: Continue ceftriaxone/cefotaxime; treat for 14 days 1
• Both penicillin and cephalosporin resistant: Continue ceftriaxone/cefotaxime PLUS vancomycin 15-20 mg/kg IV every 12 hours PLUS rifampicin 600 mg every 12 hours; treat for 14 days 1, 4

Neisseria meningitidis

• Continue ceftriaxone/cefotaxime; treat for 7 days 1

Listeria monocytogenes

• Ampicillin/amoxicillin for 21 days, potentially with gentamicin or co-trimoxazole 3

Critical Points to Remember

1. Timing is crucial: Start antibiotics within 1 hour of presentation after blood cultures are drawn, even if lumbar puncture is delayed 2

2. Resistance considerations: When using dexamethasone, the combination of ceftriaxone and rifampicin is preferred over vancomycin for resistant pneumococci, as dexamethasone reduces vancomycin penetration into CSF 4

3. Dosing considerations: For penicillin-susceptible S. pneumoniae, a ceftriaxone total daily dose of 2g may be sufficient (rather than 4g), though many institutions continue with the higher dose initially 5

4. Common pitfalls to avoid:

   • Failing to cover Listeria in patients ≥50 years or immunocompromised
   • Neglecting to add vancomycin when risk of resistant pneumococci exists
   • Delaying antibiotic administration (significantly increases mortality)
   • Not adjusting therapy based on culture results and susceptibility patterns 2

5. Travel history: Always ask about recent travel to regions with high pneumococcal resistance rates and add vancomycin or rifampicin if indicated 1