A 28-year-old woman presents with acute bacterial meningitis. CSF shows gram-positive cocci in pairs. Blood cultures are pending. What is the drug of choice for empirical treatment in this patient?

Explanation

## Drug of Choice for Bacterial Meningitis **Key Point:** Ceftriaxone is the first-line agent for empirical treatment of bacterial meningitis in adults, particularly when Streptococcus pneumoniae is suspected. ### Why Ceftriaxone? 1. **Superior CNS penetration**: Achieves adequate CSF concentrations (15–20% of serum levels) even without meningeal inflammation, and higher levels (up to 80%) when meninges are inflamed. 2. **Broad spectrum**: Covers S. pneumoniae, Neisseria meningitidis, and Listeria monocytogenes (when combined with ampicillin in older patients or immunocompromised). 3. **Bactericidal**: Rapidly kills meningeal pathogens via cell wall inhibition. 4. **Standard dosing in meningitis**: 2 g IV every 4–6 hours (higher than non-meningitis infections). ### Comparison with Other Beta-Lactams | Agent | CNS Penetration | Spectrum | Meningitis Use | |-------|-----------------|----------|----------------| | **Ceftriaxone** | Excellent (15–80%) | S. pneumoniae, N. meningitidis, L. monocytogenes (if combined) | **First-line** | | Ampicillin | Moderate (10–20%) | Gram-positive, gram-negative, Listeria | Second-line; used with cephalosporin for Listeria coverage | | Penicillin G | Poor (5–10%) | Gram-positive only; inadequate for meningitis | Obsolete for meningitis | | Cefazolin | Poor (5–10%) | Limited gram-negative coverage; poor CNS penetration | Not suitable for meningitis | **Clinical Pearl:** In patients >50 years or immunocompromised, add ampicillin to ceftriaxone to cover Listeria monocytogenes (cephalosporins do not cover Listeria). [cite:Harrison 21e Ch 373] **High-Yield:** Ceftriaxone dosing in meningitis is **double** the standard dose (2 g Q4–6H vs. 1 g Q12H for other infections).