What is the recommended treatment for suspected acute bacterial meningitis?

Treatment of Suspected Acute Bacterial Meningitis

Empiric antibiotic therapy must be initiated within 1 hour of hospital arrival in all patients with suspected acute bacterial meningitis, and should never be delayed for diagnostic procedures including lumbar puncture or CT imaging. 1, 2

Immediate Actions (Within First Hour)

• Obtain blood cultures immediately before administering antibiotics 1, 2
• Administer dexamethasone 10 mg IV either shortly before or simultaneously with the first antibiotic dose 1
• Initiate empiric antibiotics within 60 minutes of hospital entry, regardless of whether lumbar puncture has been performed 1, 2
• If lumbar puncture is delayed due to CT imaging or other reasons, start antibiotics immediately on clinical suspicion 1, 2

Empiric Antibiotic Regimens by Age and Risk Factors

Adults Under 50 Years (Immunocompetent)

Ceftriaxone 2 g IV every 12 hours OR Cefotaxime 2 g IV every 6 hours 1

• Third-generation cephalosporins provide excellent CSF penetration and cover the most common pathogens (S. pneumoniae, N. meningitidis) 1
• Alternative if severe penicillin allergy: Chloramphenicol 25 mg/kg IV every 6 hours 1

Adults 50-60 Years or Older

Ceftriaxone 2 g IV every 12 hours (or Cefotaxime 2 g IV every 6 hours) PLUS Ampicillin 2 g IV every 4 hours 1, 2

• The addition of ampicillin is essential to cover Listeria monocytogenes, which becomes increasingly common in this age group 1, 2
• Alternative for penicillin allergy: Chloramphenicol 25 mg/kg IV every 6 hours PLUS Co-trimoxazole 10-20 mg/kg (trimethoprim component) IV in four divided doses 1

Special Circumstances Requiring Additional Coverage

Add Vancomycin 15-20 mg/kg IV every 12 hours (target trough 15-20 μg/mL) OR Rifampicin 600 mg IV/PO every 12 hours if: 1

• Patient has traveled to areas with high pneumococcal penicillin resistance in the past 6 months 1
• Known local prevalence of penicillin-resistant S. pneumoniae 1
• Patient is severely immunocompromised 1

Neonates (≤28 Days)

Ampicillin 50 mg/kg IV every 6-8 hours PLUS Cefotaxime 50 mg/kg IV every 6-8 hours 1, 2

• Administer IV doses over 60 minutes in neonates to reduce risk of bilirubin encephalopathy 3
• Do NOT use ceftriaxone in neonates due to risk of kernicterus and calcium-ceftriaxone precipitation 3

Children (1 Month to 18 Years)

Ceftriaxone 50 mg/kg IV every 12 hours (maximum 2 g per dose) OR Cefotaxime 75 mg/kg IV every 6-8 hours PLUS Vancomycin 10-15 mg/kg IV every 6 hours 1, 2

Adjunctive Dexamethasone Therapy

Dexamethasone 10 mg IV every 6 hours should be administered for 4 days in all adults with suspected bacterial meningitis 1

• Start dexamethasone shortly before or with the first antibiotic dose 1
• If antibiotics have already been given, dexamethasone can still be initiated up to 12 hours after the first antibiotic dose 1
• Continue dexamethasone for 4 days if pneumococcal meningitis is confirmed or highly suspected 1
• Discontinue dexamethasone if another pathogen is identified (e.g., meningococcal, Listeria) 1

Definitive Therapy Based on Pathogen Identification

Pneumococcal Meningitis (S. pneumoniae)

• If penicillin-sensitive (MIC ≤0.06 mg/L): Continue ceftriaxone/cefotaxime OR switch to benzylpenicillin 2.4 g IV every 4 hours 1
• If penicillin-resistant but cephalosporin-sensitive: Continue ceftriaxone 2 g IV every 12 hours or cefotaxime 2 g IV every 6 hours 1
• If both penicillin and cephalosporin-resistant: Continue ceftriaxone/cefotaxime PLUS vancomycin 15-20 mg/kg IV every 12 hours PLUS rifampicin 600 mg IV/PO every 12 hours 1
• Duration: 10 days if recovered; 14 days if not recovered or if resistant organism 1

Meningococcal Meningitis (N. meningitidis)

• Continue ceftriaxone 2 g IV every 12 hours or cefotaxime 2 g IV every 6 hours 1
• Alternative: Benzylpenicillin 2.4 g IV every 4 hours 1
• If not treated with ceftriaxone, give single dose of ciprofloxacin 500 mg PO for eradication of nasopharyngeal carriage 1
• Duration: 5 days if patient has recovered 1

Listeria Meningitis (L. monocytogenes)

• Ampicillin 2 g IV every 4 hours PLUS Gentamicin (for synergy) 4
• Alternative if penicillin allergy: Co-trimoxazole 1
• Duration: Minimum 21 days 1

Critical Pitfalls to Avoid

Never delay antibiotics for imaging or lumbar puncture - this is the single most important factor affecting mortality and morbidity 1, 2, 5

Do not omit ampicillin coverage in patients ≥50 years or immunocompromised - Listeria is a critical pathogen in these populations that is NOT covered by cephalosporins 1, 2

Do not use inadequate antibiotic doses - bacterial meningitis requires high-dose therapy to achieve adequate CSF penetration 1

Do not forget blood cultures before antibiotics - this may be the only microbiological diagnosis if lumbar puncture is delayed 1, 2

Do not use ceftriaxone in neonates - risk of fatal kernicterus and calcium-ceftriaxone precipitation 3

Do not omit vancomycin in areas with pneumococcal resistance - treatment failure can occur with cephalosporins alone against resistant strains 1

Indications for CT Before Lumbar Puncture

Perform CT scan before lumbar puncture only in patients with: 1, 2

• Focal neurological deficits (excluding cranial nerve palsies)
• New-onset seizures
• Severely altered mental status (Glasgow Coma Scale <10-12)
• Severely immunocompromised state
• History of CNS disease (mass lesion, stroke, focal infection)
• Papilledema

In all cases where CT is indicated, start antibiotics BEFORE sending the patient for imaging 1, 2

Intensive Care Referral

Transfer to ICU is indicated for patients with: 1

• Rapidly evolving rash
• Glasgow Coma Scale ≤12 (or drop of >2 points)
• Cardiovascular instability or severe sepsis
• Respiratory compromise or hypoxia
• Uncontrolled seizures
• Need for specific organ support