What is the recommended treatment for bacterial meningitis?

Bacterial Meningitis Treatment

Immediate Empiric Antibiotic Therapy

Begin treatment within 1 hour of presentation with a third-generation cephalosporin plus vancomycin, adding ampicillin for patients over 50 years or those with risk factors for Listeria monocytogenes. 1, 2, 3

Age-Based Empiric Regimens

Neonates (<1 month):

• Ampicillin 50 mg/kg IV every 6-8 hours PLUS cefotaxime 50 mg/kg IV every 6-8 hours 2, 3
• Alternative: Ampicillin plus gentamicin 2.5 mg/kg IV every 8-12 hours (age-dependent) 2

Children (1 month 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, 2
• PLUS vancomycin 10-15 mg/kg IV every 6 hours (target trough 15-20 mg/mL) 2

Adults (18-50 years):

• Ceftriaxone 2g IV every 12 hours OR cefotaxime 2g IV every 4-6 hours 1, 2
• PLUS vancomycin 15-20 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) 1, 2

Adults (>50 years or immunocompromised):

• Ceftriaxone 2g IV every 12 hours OR cefotaxime 2g IV every 4-6 hours 1, 2
• PLUS vancomycin 15-20 mg/kg IV every 8-12 hours 1, 2
• PLUS ampicillin 2g IV every 4 hours (for Listeria coverage) 1, 2, 3

Adjunctive Dexamethasone Therapy

Administer dexamethasone 10 mg IV every 6 hours (0.15 mg/kg every 6 hours in children) 10-20 minutes before or simultaneously with the first antibiotic dose. 1, 2, 3

• Continue for 4 days if pneumococcal or H. influenzae meningitis is confirmed 1, 2
• Discontinue if another pathogen is identified 1
• In adults with pneumococcal meningitis, dexamethasone reduces unfavorable outcomes (26% vs 52%, P=0.006) and mortality (14% vs 34%, P=0.02) 2

Critical Caveat on Dexamethasone

Dexamethasone may reduce CSF penetration of vancomycin—when treating suspected resistant pneumococci with dexamethasone, consider adding rifampin to the regimen. 1

Pathogen-Specific Definitive Therapy (After Culture Results)

Streptococcus pneumoniae:

• Penicillin MIC <0.1 μg/mL: Switch to penicillin G 24 million units/day (divided every 4 hours) OR ampicillin 1, 2
• Penicillin MIC 0.1-1.0 μg/mL: Continue third-generation cephalosporin 1
• Penicillin MIC ≥2.0 μg/mL OR ceftriaxone MIC ≥1.0 μg/mL: Continue vancomycin PLUS third-generation cephalosporin 1
• Duration: 10-14 days 1, 2

Neisseria meningitidis:

• Penicillin-susceptible: Switch to penicillin G 24 million units/day OR continue ceftriaxone 2g every 12 hours 1, 2
• Reduced susceptibility: Continue third-generation cephalosporin 1
• Duration: 5-7 days 1, 2
• Give single dose ciprofloxacin 500mg PO for eradication 3

Haemophilus influenzae:

• β-lactamase negative: Switch to ampicillin 1
• β-lactamase positive: Continue third-generation cephalosporin 1
• Duration: 10 days 2

Listeria monocytogenes:

• Ampicillin 2g IV every 4 hours (12g total daily dose) 2, 3
• Duration: 21 days 2

Culture-negative meningitis:

• Continue empiric regimen for at least 14 days 1

Critical Timing and Diagnostic Considerations

Do not delay antibiotics for imaging or lumbar puncture—start treatment within 1 hour even if CT or LP is pending. 1, 2, 3

• Obtain blood cultures before antibiotics, but do not delay treatment beyond 1 hour 3
• If lumbar puncture is delayed, start empiric treatment immediately on clinical suspicion 3
• CSF findings (elevated WBC, decreased glucose, elevated protein) remain diagnostically useful even after antibiotics are started 3

Indications for CT Before Lumbar Puncture

Perform CT before LP if patient has: 3

• Age ≥60 years
• Immunocompromise
• History of CNS disease (mass lesion, stroke, focal infection)
• New-onset seizures
• Altered mental status or GCS ≤12
• Focal neurological deficits
• Papilledema

Critical Care Considerations

Transfer to ICU if patient has: 1, 3

• Rapidly evolving rash or limb ischemia
• GCS ≤12 (or drop >2 points)
• Cardiovascular instability or acid/base disturbance
• Hypoxia or respiratory compromise
• Frequent or uncontrolled seizures
• Requirement for monitoring or specific organ support

Strongly consider intubation if GCS <12. 1, 3

Common Pitfalls to Avoid

Never use vancomycin as monotherapy for bacterial meningitis, even for highly resistant pneumococcal strains. 1

Never use rifampin as monotherapy due to rapid development of resistance. 1

Never fail to cover Listeria in patients >50 years or immunocompromised—this requires ampicillin addition. 2, 3

Never delay antibiotics for imaging—delayed treatment is strongly associated with death and poor neurological outcomes. 1, 3

Never use suboptimal antibiotic doses that don't achieve adequate CSF penetration. 3

Dosing Adjustments for Renal Impairment (Adults)

Creatinine clearance >50 mL/min: Standard dosing every 8 hours 1

Creatinine clearance 26-50 mL/min: Standard dose every 12 hours 1

Creatinine clearance 10-25 mL/min: Half the standard dose every 12 hours 1

Creatinine clearance <10 mL/min: Half the standard dose every 24 hours 1