## Empirical Treatment of Bacterial Meningitis **Key Point:** Ceftriaxone is the first-line empirical agent for bacterial meningitis in adults, covering the most common pathogens (Streptococcus pneumoniae, Neisseria meningitidis, and Listeria monocytogenes with adequate CNS penetration). ### Rationale for Ceftriaxone **High-Yield:** Ceftriaxone achieves excellent CSF penetration (15–20% of serum levels in inflamed meninges) and covers: - *Streptococcus pneumoniae* (most common in India) - *Neisseria meningitidis* - Gram-negative bacilli (if Listeria coverage added) **Clinical Pearl:** The CSF findings (low glucose, elevated protein, neutrophilic pleocytosis) and gram-positive diplococci are classic for pneumococcal meningitis—ceftriaxone is the standard first-line choice. ### Dosing in Meningitis **Key Point:** Higher doses required for meningitis: - Ceftriaxone: 2 g IV every 4–6 hours (or 4 g every 4 hours in severe cases) - NOT the standard 1–2 g for other infections ### When to Add Vancomycin **Warning:** Vancomycin is added empirically ONLY if: - Penicillin-resistant *S. pneumoniae* is suspected (e.g., immunocompromised, prior antibiotics) - Cephalosporin allergy - In this case, gram-positive diplococci + typical CSF profile = pneumococcal meningitis → ceftriaxone monotherapy is sufficient ### Why Not Penicillin G Alone? **High-Yield:** Although penicillin G covers pneumococci and meningococci, resistance rates (especially in India) and inconsistent CSF penetration make it inferior to ceftriaxone as empirical monotherapy. ### Why Not Chloramphenicol? **Warning:** Chloramphenicol is an older agent with: - Unpredictable CSF penetration - Bone marrow toxicity (aplastic anemia) - No longer recommended in modern guidelines - Reserved only for severe penicillin/cephalosporin allergy [cite:Harrison 21e Ch 297]
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