Antibiotic choice is affected by complicated factors:

• etiologic bacterial species
• blood-brain barrier penetration
• antibacterial activity within purulent CSF
• drug metabolism
• potential drug interactions
• host defense status

The following general guidelines are well developed, however:

Organism	Antibiotic
Streptococcus pneumoniae
Penicillin-sensitive	Penicillin G or ampicillin
Partial penicillin-sensitive	Third-generation cephalosporin
Penicillin-resistant	Vancomycin + third-generation cephalosporin
Neisseria meningitidis	Penicillin G or ampicillin
Haemophilus influenzae
Beta-lactamase negative	Ampicillin
Beta-lactamase positive	Third-generation cephalosporin
Enterobacteriaceae	Third-generation cephalosporin
Pseudomonas aeruginosa	Ceftazidime
Listeria monocytogenes	Penicillin G or ampicillin
Staphylococcus aureus
Methicillin-sensitive	Nafcillin or oxacillin
Methicillin-resistant	Vancomycin
Staphylococcus epidermidis	Vancomycin

Table adapted from KL Roos, AR Tunkel, WM Scheld. Acute bacterial meningitis in children and adults. In WM Scheld, RJ Whitley, DT Durack (eds), Infections of the Central Nervous System. Philadelphia: Lippincott–Raven, 1997;336–401.
Adapted from: Goldstein MA and Harden CL. Infectious states. In: Ettinger AB and Devinsky O, eds. Managing epilepsy and co-existing disorders. Boston: Butterworth-Heinemann; 2002;83-133.
With permission from Elsevier (www.elsevier.com).
Reviewed and revised March 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.