What is the initial treatment for bacterial meningitis?

Initial Treatment for Bacterial Meningitis

Antibiotic therapy must be initiated immediately upon clinical suspicion of bacterial meningitis, with administration occurring within 1 hour of hospital arrival, and should never be delayed for imaging or lumbar puncture. 1

Immediate Actions (First Hour)

• Obtain blood cultures before antibiotics whenever possible, but do not delay treatment if this causes any delay 1
• Start empiric antibiotics immediately if lumbar puncture is delayed for any reason (need for CT scan, coagulopathy, hemodynamic instability) 2, 1
• Administer dexamethasone 10 mg IV before or with the first antibiotic dose in all adults and children (0.15 mg/kg in children, maximum 10 mg) 2, 1
• Dexamethasone can still be given up to 4 hours after antibiotics are started if not given initially 2

Empiric Antibiotic Regimens by Age and Risk Factors

Neonates (≤28 days)

• Ampicillin 200-300 mg/kg/day IV divided every 6-8 hours PLUS cefotaxime 200 mg/kg/day IV divided every 6 hours 1, 3
• This covers Group B Streptococcus, E. coli, and Listeria monocytogenes 3
• Ceftriaxone is contraindicated in neonates due to risk of bilirubin encephalopathy and calcium precipitation 4

Children (>28 days) and Adults <50 years

• Ceftriaxone 2 g IV every 12 hours (or 4 g/day) OR cefotaxime 2 g IV every 6 hours PLUS vancomycin 15-20 mg/kg IV every 8-12 hours 2, 1
• In children: ceftriaxone 100 mg/kg/day (max 4 g/day) or cefotaxime 300 mg/kg/day plus vancomycin 60 mg/kg/day 5
• This covers S. pneumoniae (including resistant strains), N. meningitidis, and H. influenzae 2

Adults ≥50 years or Immunocompromised Patients

• Ceftriaxone 2 g IV every 12 hours PLUS vancomycin 15-20 mg/kg IV every 8-12 hours PLUS ampicillin 2 g IV every 4 hours 2, 1
• The ampicillin addition is critical for Listeria monocytogenes coverage, which occurs in 1.5% of adults <50 without risk factors but is much more common in older or immunocompromised patients 2
• Risk factors for Listeria include: age >50, diabetes, immunosuppressive drugs, cancer, alcoholism, pregnancy 2, 1

High Pneumococcal Resistance Areas

• Add vancomycin or rifampicin to third-generation cephalosporins when local resistance rates show decreased susceptibility (MIC >0.5 mg/L for penicillin or MIC >2 mg/L for cephalosporins) 2
• Vancomycin is preferred over rifampicin as the first addition 2

Adjunctive Dexamethasone Therapy

• Dexamethasone 10 mg IV every 6 hours for 4 days in adults (0.15 mg/kg every 6 hours for 4 days in children) 2
• Must be given before or with the first antibiotic dose for maximum benefit 2, 1
• Reduces mortality, hearing loss, and neurologic sequelae, particularly in pneumococcal meningitis 2
• Stop dexamethasone if bacterial meningitis is ruled out or if the pathogen is identified as something other than S. pneumoniae or H. influenzae, though some experts continue it regardless of pathogen 2

Critical Pitfalls to Avoid

• Never delay antibiotics for CT imaging - if CT is needed due to concern for elevated intracranial pressure (altered mental status, focal deficits, papilledema, immunocompromise, age ≥60, seizures), give antibiotics first, then image 1
• Never delay antibiotics for lumbar puncture - CSF findings remain diagnostic even after antibiotics are started, though culture yield decreases 1
• Do not forget Listeria coverage in patients ≥50 years or with any immunocompromising condition - this is the most common fatal error 2, 1
• Do not use inadequate dosing - meningitis requires higher doses than other infections to achieve adequate CSF penetration (e.g., ceftriaxone 4 g/day, not 2 g/day) 2, 4
• Do not use ceftriaxone in neonates due to risk of kernicterus and calcium-ceftriaxone precipitation 4

Special Considerations

• In neonates, infuse antibiotics over 60 minutes to reduce risk of bilirubin encephalopathy 4
• Implement respiratory isolation immediately until meningococcal disease is excluded or patient receives 24 hours of appropriate antibiotics 6
• Consider ICU admission for patients with GCS ≤12, rapidly evolving rash, cardiovascular instability, or severe sepsis 6
• Treatment duration is typically 10-14 days for pneumococcal meningitis, 7 days for meningococcal, and 21 days for Listeria 2, 5