Which statement best describes empiric therapy for suspected meningitis in adults?

• A. Ceftriaxone plus vancomycin is an appropriate empiric therapy for adults with suspected meningitis, without ampicillin
• B. Ampicillin alone is the empiric therapy
• C. Vancomycin + a third-generation cephalosporin, with ampicillin added for Listeria in older or immunocompromised
• D. Dexamethasone alone is sufficient therapy

Answer: (C)

Empiric therapy for suspected meningitis in adults aims for rapid, broad coverage of the most likely bacteria, with additional coverage for Listeria in patients who are older or immunocompromised. Vancomycin targets penicillin-resistant strains like resistant Streptococcus pneumoniae, while a third-generation cephalosporin covers Neisseria meningitidis and many pneumococci. However, neither vancomycin nor the cephalosporin reliably covers Listeria monocytogenes, which is a key risk in adults over 50 or those with weakened immune systems. Adding ampicillin specifically addresses that gap, ensuring coverage of Listeria. Dexamethasone can be used as an adjunct to reduce inflammation-related complications but does not substitute for antibiotics. Ampicillin alone would miss a broad range of other pathogens, and dexamethasone alone provides no antimicrobial activity. So, the regimen that pairs vancomycin with a third-generation cephalosporin and includes ampicillin for older or immunocompromised patients best captures appropriate empiric therapy.