Treatment Approach for Bacterial vs Viral Meningitis
Immediate Management: Treat as Bacterial Until Proven Otherwise
When bacterial meningitis is suspected, initiate empiric antibiotics within 1 hour of presentation—do not delay for imaging or lumbar puncture. 1, 2 Blood cultures must be obtained before antibiotics, but antibiotic administration should never be delayed beyond 1 hour. 1, 2
Key Principle: The Critical Difference
The fundamental distinction in management is that bacterial meningitis requires immediate empiric antibiotics because delay is strongly associated with increased mortality and poor neurological outcomes, while viral meningitis is typically self-limited and requires only supportive care. 1 However, you cannot reliably distinguish bacterial from viral meningitis on initial presentation alone, so empiric antibacterial coverage is mandatory until bacterial etiology is excluded. 1
Empiric Antibiotic Therapy by Age Group
Neonates (<1 month)
- Ampicillin 50 mg/kg IV every 6-8 hours PLUS cefotaxime 50 mg/kg IV every 6-8 hours 2
- Alternative: Ampicillin plus gentamicin 2.5 mg/kg IV every 8-12 hours (dose adjusted by age) 2
- Ceftriaxone is contraindicated in neonates due to risk of bilirubin encephalopathy and precipitation with calcium-containing solutions 3
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 2
- PLUS vancomycin 10-15 mg/kg IV every 6 hours (target trough 15-20 mg/mL) 2
Adults <50 years without Listeria risk factors
- Ceftriaxone 2g IV every 12 hours OR cefotaxime 2g IV every 4-6 hours 4, 2
- PLUS vancomycin 15-20 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) 4, 2
- Vancomycin addition is critical in regions with elevated pneumococcal penicillin resistance 4
Adults ≥50 years or immunocompromised
- Same regimen as above PLUS ampicillin 2g IV every 4 hours (12g total daily dose) 4, 2
- The ampicillin addition provides essential Listeria monocytogenes coverage 4, 2
- Risk factors for Listeria include: age >50, diabetes, immunosuppressive drugs, cancer, and other immunocompromising conditions 4, 1
Adjunctive Dexamethasone Therapy
Administer dexamethasone 10 mg IV every 6 hours (or 0.15 mg/kg every 6 hours in children) 10-20 minutes before or simultaneously with the first antibiotic dose. 1, 2 This applies to all suspected bacterial meningitis cases. 2
- Continue for 2-4 days if pneumococcal or H. influenzae meningitis is confirmed 2
- In pneumococcal meningitis, dexamethasone reduces unfavorable outcomes (26% vs 52%, P=0.006) and mortality (14% vs 34%, P=0.02) 2
- Discontinue dexamethasone if Pseudomonas is identified, as it only benefits pneumococcal and H. influenzae meningitis 5
When to Perform CT Before Lumbar Puncture
Obtain CT before LP only if the patient has: 1
- Age ≥60 years
- Immunocompromised state
- History of CNS disease (mass lesion, stroke, focal infection)
- New-onset seizures
- Altered mental status (Glasgow Coma Scale <10)
- Focal neurological deficits
- Papilledema
Critical pitfall: Never delay antibiotics for imaging. Start treatment within 1 hour even if CT or LP is pending. 1, 2 If CT is indicated, perform it after antibiotics have been initiated, and only proceed with LP if CT shows no mass effect or elevated intracranial pressure. 1
Pathogen-Specific Definitive Therapy
Once culture results and susceptibilities are available, narrow therapy appropriately:
Streptococcus pneumoniae (Penicillin-Sensitive)
- Penicillin G 24 million units/day IV (divided every 4 hours) OR continue ceftriaxone 2g IV every 12 hours 2
- Duration: 10-14 days 4, 2
- If ceftriaxone-resistant (MIC >2 mg/L), continue ceftriaxone plus vancomycin or rifampicin 4, 6
Neisseria meningitidis
- Penicillin G 24 million units/day IV OR ceftriaxone 2g IV every 12 hours 2
- Duration: 5-7 days 2
- Add single dose ciprofloxacin 500mg PO for eradication 1
Listeria monocytogenes
- Ampicillin 2g IV every 4 hours (12g total daily dose) 2
- Duration: 21 days 2
- Alternative: Add gentamicin for synergy in severe cases 7
Haemophilus influenzae
Staphylococcus aureus
- Flucloxacillin, nafcillin, or oxacillin for methicillin-sensitive strains 4
- Vancomycin for methicillin-resistant strains 4
- Consider adding rifampicin for synergy 4
Pseudomonas aeruginosa
- Ceftazidime 2g IV every 8 hours PLUS tobramycin 3-5 mg/kg/day IV divided every 8 hours 5
- Duration: 21 days (do not shorten even if CSF sterilizes early) 5
- If shunt-related, the shunt must typically be removed for cure 5
Viral Meningitis Management
Viral meningitis requires supportive care only—no antibiotics are indicated once bacterial etiology is excluded. 8
Distinguishing Features
- CSF typically shows lymphocytic predominance (though early viral meningitis may show neutrophils) 8
- Critical distinction: Hypoglycorrhachia (low CSF glucose) strongly suggests bacterial etiology and mandates treating for bacterial meningitis first 1
- Normal or mildly elevated CSF glucose suggests viral etiology 8
- Elevated serum C-reactive protein and procalcitonin are associated with bacterial meningitis 4
When to Stop Empiric Antibiotics
- CSF shows lymphocytic predominance with normal glucose
- Gram stain negative
- Bacterial cultures negative at 48-72 hours
- Clinical improvement without antibiotics
- PCR or other testing confirms viral pathogen 4, 8
Common Pitfalls to Avoid
Delaying antibiotics for imaging: Start treatment within 1 hour regardless of imaging needs 1, 2
Inadequate Listeria coverage: Always add ampicillin for patients >50 years or immunocompromised 4, 2
Insufficient antibiotic dosing: Use high-dose regimens to achieve adequate CSF penetration 2, 3
Neglecting blood cultures: Obtain before antibiotics, but never delay treatment 1, 2
Premature discontinuation of therapy: Complete full treatment duration based on pathogen (5-21 days depending on organism) 2
Forgetting dexamethasone: Administer before or with first antibiotic dose for maximum benefit 1, 2