Are cephalosporins active against Listeria monocytogenes?

• A. No
• B. Yes
• C. Not specified
• D. Only some generations

Answer: (A)

Cephalosporins are not active against Listeria monocytogenes. Listeria is intrinsically resistant to many beta-lactams, and cephalosporins in particular have poor activity against it because of limited binding to its penicillin-binding proteins and inadequate intracellular penetration where the organism can reside. In clinical practice, Listeria meningitis or infection is treated with ampicillin or penicillin G (often with gentamicin for synergy), not a cephalosporin. Even the broader-spectrum generations do not reliably cover Listeria, so the lack of activity is consistent across cephalosporins.