Bacterial Meningitis Treatment
Immediate empiric treatment with a third-generation cephalosporin (ceftriaxone 2g IV every 12 hours or cefotaxime 2g IV every 4-6 hours) plus vancomycin (15-20 mg/kg every 8-12 hours) should be initiated within 1 hour of clinical suspicion, with ampicillin (2g IV every 4 hours) added for patients over 50 years or those with risk factors for Listeria. 1
Immediate Management Priorities
Do not delay antibiotics for imaging or lumbar puncture - this is the most critical pitfall that worsens outcomes. 1 Treatment must begin immediately upon clinical suspicion, even before diagnostic confirmation.
Adjunctive Dexamethasone Therapy
- Administer dexamethasone 10 mg IV every 6 hours, with the first dose given shortly before or simultaneously with the first antibiotic dose 1
- Continue for 4 days if pneumococcal meningitis is confirmed or suspected; discontinue if another pathogen is identified 1
- Important caveat: Dexamethasone may reduce CSF penetration of vancomycin - when using dexamethasone with suspected resistant pneumococci, strongly consider adding rifampin to the regimen 1
Age-Stratified Empiric Antibiotic Regimens
Neonates (0-3 months)
- Ampicillin 50 mg/kg IV every 8 hours (age <1 week) PLUS cefotaxime 50 mg/kg IV every 8 hours 1
- Alternative: Ampicillin plus an aminoglycoside 1
Children (3 months to 18 years)
- Ceftriaxone 50 mg/kg IV every 12 hours (maximum 2g every 12 hours) OR cefotaxime 75 mg/kg IV every 6-8 hours 1
- PLUS vancomycin or rifampin 1
Adults (18-50 years)
- Ceftriaxone 2g IV every 12 hours (or 4g every 24 hours) OR cefotaxime 2g IV every 4-6 hours 1
- PLUS vancomycin or rifampin 1
Adults (>50 years or Listeria risk factors)
- Same cephalosporin regimen as younger adults 1
- PLUS vancomycin or rifampin 1
- PLUS ampicillin 2g IV every 4 hours to cover Listeria monocytogenes 1
Pathogen-Specific Treatment (After Identification)
Streptococcus pneumoniae
Treatment depends on susceptibility testing:
- Penicillin MIC <0.1 μg/mL: Switch to penicillin G or ampicillin alone 1
- Penicillin MIC 0.1-1.0 μg/mL: Continue third-generation cephalosporin alone 1
- Penicillin MIC ≥2.0 μg/mL OR ceftriaxone/cefotaxime MIC ≥1.0 μg/mL: Continue vancomycin PLUS third-generation cephalosporin 1
Critical warning: Vancomycin should never be used as monotherapy, even for highly resistant strains 1. Animal studies demonstrate that ceftriaxone combined with vancomycin achieves higher CSF sterilization rates than monotherapy 2.
- Duration: 10-14 days 2, 1
- Addition of rifampin may be considered based on in vitro susceptibility patterns, though clinical evidence is limited 2
Neisseria meningitidis
- Penicillin susceptible: Switch to penicillin G or ampicillin 1
- Reduced penicillin susceptibility: Continue third-generation cephalosporin 1
- Up to 80% of meningococcal strains may have reduced penicillin susceptibility in some regions, though most respond well to penicillin therapy 2
- Duration: 7 days 2, 1
Haemophilus influenzae
- β-lactamase negative: Switch to ampicillin 1
- β-lactamase positive: Continue third-generation cephalosporin 1
- Meropenem is FDA-approved for H. influenzae meningitis in pediatric patients ≥3 months 3
Staphylococcus aureus
- Methicillin-susceptible: Flucloxacillin, nafcillin, or oxacillin; consider combination with fosfomycin or rifampin 2
- Methicillin-resistant (MRSA): Vancomycin is recommended 2
- Vancomycin-resistant (MIC >2 μg/mL): Linezolid may be chosen 2
- Rifampin can be added as supplementary therapy but must never be used as monotherapy due to rapid resistance development 2, 1
- Duration: At least 14 days 2
Culture-Negative Meningitis
Continue empiric treatment for at least 14 days when CSF is suggestive of bacterial meningitis but cultures and PCR remain negative 2, 1. Duration may need extension depending on clinical response 2.
Critical Care Indications
Transfer to intensive care for: 1
- Rapidly evolving rash or limb ischemia
- Glasgow Coma Scale (GCS) ≤12 or drop >2 points
- Cardiovascular instability or acid/base disturbance
- Hypoxia or respiratory compromise
- Frequent or uncontrolled seizures
- Altered mental state requiring monitoring or organ support
Consider intubation for GCS <12 1
Key Pitfalls to Avoid
- Never delay antibiotics - waiting for imaging or LP results is associated with poor outcomes 1
- Never use vancomycin alone - always combine with a cephalosporin for pneumococcal coverage 1
- Never use rifampin as monotherapy - resistance develops rapidly 2, 1
- Don't forget ampicillin in older adults - Listeria coverage is essential in patients >50 years 1
- Account for dexamethasone-vancomycin interaction - consider adding rifampin when using both agents 1
Dosing in Renal Impairment (Adults)
For creatinine clearance ≤50 mL/min, adjust dosing as follows: 3
- CrCl 26-50 mL/min: Recommended dose every 12 hours
- CrCl 10-25 mL/min: Half recommended dose every 12 hours
- CrCl <10 mL/min: Half recommended dose every 24 hours