What are the recommended antibiotics for treating nosocomial meningitis?

Recommended Antibiotics for Nosocomial Meningitis

For nosocomial meningitis, the recommended empiric antibiotic regimen is a combination of meropenem plus vancomycin, with consideration for adding an aminoglycoside administered intraventricularly in cases of suspected or confirmed carbapenem-resistant gram-negative pathogens. 1, 2

Pathogen Considerations in Nosocomial Meningitis

• Nosocomial meningitis pathogens differ significantly from community-acquired meningitis, with coagulase-negative Staphylococcus (40.9%) and Acinetobacter species (32.5%) being the most common causative organisms 3
• Gram-negative bacteria are isolated in approximately 52.3% of post-operative nosocomial meningitis cases and are associated with higher mortality rates compared to gram-positive cases 4
• Staphylococcus aureus is another significant pathogen in nosocomial meningitis with a mortality rate of 55% 1
• External ventricular drains (EVD) are associated with 85.7% of nosocomial meningitis cases, representing a major risk factor 3

Empiric Antibiotic Regimen

• Meropenem (2g IV every 8 hours) is indicated for the treatment of bacterial meningitis and has excellent CNS penetration 5
• Vancomycin should be added to the empiric regimen to cover methicillin-resistant Staphylococcus aureus (MRSA) and other resistant gram-positive organisms 6
• Standard penicillin monotherapy is inadequate for nosocomial meningitis, with studies showing it would only cover 77% of cases 1
• A combination of penicillin plus ceftriaxone would cover 97% of community-acquired cases but would still miss certain nosocomial pathogens like Pseudomonas species and MRSA 1

Special Considerations for Resistant Organisms

• For carbapenem-resistant gram-negative bacteria, particularly Acinetobacter species, intraventricular administration of antibiotics should be considered 2
• Intraventricular options include:
  • Colistimethate sodium (10 mg/day) 4
  • Amikacin (10 mg/day) 4
  • Gentamicin (10 mg/day) 4
• Clinical and microbiological success with intraventricular therapy has been reported in 53% of cases with carbapenem-resistant gram-negative infections 4

Duration of Treatment

• For nosocomial meningitis, the mean intravenous treatment duration is approximately 21.4 days 4
• When intraventricular therapy is required, the mean duration is approximately 17.6 days 4

Prognostic Factors and Management Considerations

• Poor prognostic factors include:
  • Presence of concurrent septic shock 4
  • Persistent external ventricular drainage 4
• Early removal of EVD is strongly recommended in cases of suspected nosocomial meningitis to improve outcomes 3
• Inadequate empiric antibiotic coverage is common with Acinetobacter infections (37% of cases receive inappropriate initial therapy) 3

Common Pitfalls to Avoid

• Relying on ceftazidime or cefepime alone for gram-negative coverage in nosocomial meningitis - pharmacodynamic studies suggest these will achieve therapeutic targets against fewer than 10% of contemporary Acinetobacter isolates 2
• Delaying the removal of infected neurosurgical hardware, which significantly worsens prognosis 3, 2
• Using tigecycline for carbapenem-resistant Acinetobacter meningitis is not recommended due to poor pharmacodynamic properties 2
• Using intravenous polymyxins alone without intraventricular administration for carbapenem-resistant infections 2