What is the recommended empiric treatment regimen for adult meningitis?

Empiric Treatment for Adult Bacterial Meningitis

All adults with suspected bacterial meningitis should immediately receive ceftriaxone 2g IV every 12 hours or cefotaxime 2g IV every 6 hours as the cornerstone of empiric therapy. 1

Core Empiric Regimen by Patient Population

Standard Adult (<60 years, immunocompetent)

• Ceftriaxone 2g IV every 12 hours OR Cefotaxime 2g IV every 6 hours 1
• This provides coverage for Streptococcus pneumoniae and Neisseria meningitidis, the most common pathogens 1

Adults ≥60 Years of Age

• Add Ampicillin/Amoxicillin 2g IV every 4 hours to the cephalosporin regimen 1
• This addition covers Listeria monocytogenes, which becomes increasingly prevalent in older adults 1

Immunocompromised Patients

• Triple therapy required: Ceftriaxone/Cefotaxime PLUS Ampicillin 2g IV every 4 hours PLUS Vancomycin 15-20 mg/kg IV every 12 hours 2
• Immunocompromised states include diabetes, alcohol misuse, malignancy, immunosuppressive medications, and organ transplantation 1, 2
• The triple regimen covers common pathogens plus Listeria and resistant pneumococci 2

Nosocomial Meningitis

• Vancomycin 15-20 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) PLUS an anti-pseudomonal beta-lactam 3
• Anti-pseudomonal options: Cefepime 2g IV every 8 hours, Ceftazidime 2g IV every 8 hours, or Meropenem 2g IV every 8 hours 3
• Penicillin monotherapy is explicitly inappropriate for nosocomial cases due to resistant organisms 3

Special Circumstances Requiring Additional Coverage

Recent Travel to Areas with Penicillin-Resistant Pneumococci

• Add Vancomycin 15-20 mg/kg IV every 12 hours OR Rifampicin 600mg IV/PO every 12 hours to the cephalosporin 1
• This applies if the patient has been to high-resistance areas within the last 6 months 1
• Vancomycin should never be used alone due to poor CSF penetration, especially with concurrent dexamethasone 1
• Target vancomycin trough levels of 15-20 mg/L 1

Severe Penicillin/Cephalosporin Allergy (Anaphylaxis History)

• Chloramphenicol 25 mg/kg IV every 6 hours 1, 2
• For immunocompromised patients with allergy: Add Co-trimoxazole 10-20 mg/kg (trimethoprim component) in four divided doses 1, 2

Critical Timing Considerations

Antibiotic administration must occur within 2 hours of hospital presentation to optimize outcomes and reduce mortality 1. Delays beyond 2 hours are associated with worse prognosis 1.

• Antibiotics should be given immediately if lumbar puncture is delayed for any reason (CT scan, coagulopathy correction) 1
• Do not wait for CSF results to initiate therapy 1

Common Pitfalls to Avoid

• Never use penicillin monotherapy for nosocomial meningitis, immunocompromised patients, or those from high-resistance areas 1, 3
• Never use single-agent therapy for Pseudomonas infections - combination therapy is mandatory 3
• Never use ampicillin as monotherapy for gram-negative bacteria before susceptibility results 1
• Never administer inadequate doses - using less than 50% of recommended dosing contributes to treatment failure 1
• Never use vancomycin alone - it has poor CSF penetration and must be combined with other agents 1

Definitive Therapy Based on Culture Results

Streptococcus pneumoniae Identified

• Continue ceftriaxone 2g IV every 12 hours or cefotaxime 2g IV every 6 hours for 10-14 days 1
• If penicillin-sensitive (MIC ≤0.06 mg/L): May switch to benzylpenicillin 2.4g IV every 4 hours 1
• If both penicillin and cephalosporin resistant: Continue ceftriaxone/cefotaxime PLUS vancomycin 15-20 mg/kg every 12 hours PLUS rifampicin 600mg every 12 hours for 14 days 1
• Recent evidence suggests 2g daily ceftriaxone may be adequate for highly susceptible strains, though 4g daily remains standard 4

Neisseria meningitidis Identified

• Continue ceftriaxone 2g IV every 12 hours or cefotaxime 2g IV every 6 hours for 5-7 days 1
• Alternative: Benzylpenicillin 2.4g IV every 4 hours 1
• Add single dose ciprofloxacin 500mg PO if patient did not receive ceftriaxone (to eliminate nasopharyngeal carriage) 1

Listeria monocytogenes Identified

• Continue ampicillin 2g IV every 4 hours for 21 days 1, 2
• Gentamicin is no longer recommended based on recent evidence 1

Haemophilus influenzae Identified

• Continue ceftriaxone 2g IV every 12 hours or cefotaxime 2g IV every 6 hours for 10 days 1

Enterobacteriaceae Identified

• Continue ceftriaxone/cefotaxime and seek specialist advice regarding local resistance patterns 1
• If ESBL suspected: Meropenem 2g IV every 8 hours for 21 days 1

Administration Considerations

• Ceftriaxone should be infused over 30 minutes in adults 5
• In neonates, infuse over 60 minutes to reduce bilirubin encephalopathy risk 5
• Never mix ceftriaxone with calcium-containing solutions - precipitation can occur 5
• Vancomycin trough monitoring is essential - target 15-20 mg/L 1, 2

Duration of Therapy Summary

• Meningococcal disease: 5-7 days if recovered 1
• Pneumococcal meningitis: 10-14 days 1, 2
• Listeria meningitis: 21 days 1, 2
• Haemophilus influenzae: 10 days 1
• Enterobacteriaceae: 21 days 1
• Unknown pathogen with recovery by day 10: May discontinue 1