What is the empirical treatment regimen for meningitis?

Empirical Treatment for Bacterial Meningitis

Start ceftriaxone 2g IV every 12 hours (or cefotaxime 2g IV every 4-6 hours) immediately within 1 hour of presentation for all adults, adding ampicillin 2g IV every 4 hours if age ≥60 years or immunocompromised, and adding vancomycin 15-20 mg/kg IV every 8-12 hours if recent travel to areas with penicillin-resistant pneumococci or local resistance rates are elevated. 1, 2

Critical Timing Principle

• Antibiotic administration must occur within 1 hour of hospital presentation and should never be delayed for lumbar puncture or CT imaging. 1, 2
• Obtain blood cultures before antibiotics, but this should not delay treatment beyond the 1-hour window. 2
• If imaging is indicated (focal neurologic deficits, new-onset seizures, GCS <10, or severely immunocompromised state), start antibiotics immediately before imaging. 2

Age-Based Empirical Regimens

Neonates (<1 Month Old)

• Ampicillin 2g IV every 4 hours PLUS cefotaxime 50 mg/kg IV (age <1 week) to cover Group B Streptococcus, E. coli, and Listeria monocytogenes. 1, 3
• Alternative: Ampicillin plus an aminoglycoside (gentamicin) if cefotaxime is unavailable. 1, 3
• Duration: 14-21 days for Group B Streptococcus or Listeria, at least 21 days for gram-negative enteric bacilli. 3

Children and Adults Age 1 Month to <60 Years (Immunocompetent)

• Ceftriaxone 2g IV every 12 hours OR cefotaxime 2g IV every 4-6 hours provides coverage for Streptococcus pneumoniae and Neisseria meningitidis, the most common pathogens in this population. 1, 2
• This regimen is sufficient if local S. pneumoniae resistance rates to penicillin are low (<2% with MIC >2 mg/L). 1

Adults Age ≥60 Years or Immunocompromised (Any Age)

• Add ampicillin 2g IV every 4 hours to the cephalosporin regimen to cover Listeria monocytogenes. 1, 2, 4
• Risk factors for Listeria include: diabetes mellitus, immunosuppressive drugs (including methotrexate), cancer, alcohol misuse, and other immunocompromising conditions. 1, 2, 4
• This is the most commonly missed coverage—do not omit ampicillin in these populations. 2

Additional Coverage for Penicillin-Resistant Pneumococci

• Add vancomycin 15-20 mg/kg IV every 8-12 hours (targeting trough concentrations of 15-20 μg/mL) if the patient has traveled within the past 6 months to areas with high rates of penicillin-resistant S. pneumoniae or if local resistance rates are elevated. 1, 2
• Alternative: Rifampicin 600 mg IV/PO every 12 hours can be used instead of vancomycin. 1, 2
• Animal studies demonstrate that ceftriaxone combined with either vancomycin or rifampicin results in higher CSF sterilization rates compared to ceftriaxone monotherapy against resistant strains. 1, 5, 6

Post-Neurosurgical or CSF Shunt-Related Meningitis

• Vancomycin 15-20 mg/kg IV every 12 hours PLUS one of the following: ceftazidime 2g IV every 6 hours, cefepime 2g IV every 8 hours, or meropenem 2g IV every 8 hours to cover Staphylococcus aureus (including MRSA), coagulase-negative staphylococci, and Pseudomonas aeruginosa. 1, 7
• Consider adding rifampicin 600 mg IV/orally every 12 hours for CSF shunt infections with staphylococci, especially if the shunt cannot be removed. 7
• Duration: 10-14 days for uncomplicated cases with good clinical response. 7

Pathogen-Specific De-escalation After Culture Results

Streptococcus pneumoniae

• Continue ceftriaxone 2g IV every 12 hours or cefotaxime 2g IV every 4-6 hours for 10-14 days total. 1, 2
• If penicillin-sensitive (MIC ≤0.06 mg/L), switch to benzylpenicillin 2.4g IV every 4 hours. 2, 7
• If penicillin and cephalosporin-resistant, continue ceftriaxone or cefotaxime PLUS vancomycin PLUS rifampicin 600 mg twice daily. 7

Neisseria meningitidis

• Continue ceftriaxone 2g IV every 12 hours or cefotaxime 2g IV every 6 hours for 5-7 days total. 1, 2
• Give a single dose of 500 mg ciprofloxacin orally to eliminate throat carriage. 2

Listeria monocytogenes

• Continue ampicillin 2g IV every 4 hours for 21 days total. 1, 2, 4
• Alternative: Penicillin G can be used if ampicillin is unavailable. 1

Haemophilus influenzae

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

Gram-Negative Bacilli (Enterobacteriaceae)

• Continue ceftriaxone 2g IV every 12 hours or cefotaxime 2g IV every 6 hours for 21 days. 2
• If ESBL organism suspected, switch to meropenem 2g IV every 8 hours. 2

Staphylococcus aureus

• Methicillin-susceptible: Nafcillin or oxacillin; alternative: vancomycin or meropenem. 7
• Methicillin-resistant (MRSA): Vancomycin, consider adding rifampicin 600 mg IV/orally every 12 hours. 7
• Duration: 14 days. 7

Common Pitfalls to Avoid

• Never delay antibiotics while waiting for CT imaging or lumbar puncture—if imaging is indicated, start antibacterial therapy immediately before imaging. 1, 2
• Do not omit ampicillin in patients ≥60 years or immunocompromised—Listeria coverage is essential and frequently missed. 2, 4
• Avoid inadequate dosing—use high doses to ensure adequate CSF penetration (ceftriaxone 2g every 12 hours, not lower doses). 2
• Do not stop antibacterial therapy prematurely based on clinical improvement alone—complete the full pathogen-specific duration. 2
• Repeat CSF examination at 48-72 hours after initiation of therapy in neonates to ensure sterilization. 3

Monitoring

• Monitor clinical response and consider repeat CSF cultures in treatment-resistant cases. 4
• Monitor vancomycin trough levels to maintain 15-20 μg/mL. 1, 4, 7
• Monitor for drug toxicity, especially with vancomycin and aminoglycosides. 4
• All neonates should have hearing and development monitored serially, with the first audiologic evaluation 4-6 weeks after resolution of meningitis. 3