For treating Listeria monocytogenes infection, what is the first-line treatment?

Ampicillin is the first-line treatment for Listeria monocytogenes infection due to its effectiveness against this particular pathogen. Listeria is a type of bacteria that can cause serious infections, particularly in vulnerable populations such as the elderly, pregnant women, and those with weakened immune systems.

Ampicillin is a penicillin-type antibiotic that works by inhibiting bacterial cell wall synthesis, leading to cell lysis and death. It has excellent activity against Listeria monocytogenes, making it the preferred choice in treating infections caused by this organism.

Gentamicin, while it can be used in combination with ampicillin to enhance efficacy, is not typically the first-line treatment on its own for Listeria infections. Vancomycin is primarily used for gram-positive infections resistant to other antibiotics but does not typically cover Listeria effectively. Cephalexin, a first-generation cephalosporin, is not effective against Listeria and is used primarily for treating skin and soft tissue infections caused by other bacteria.

Thus, ampicillin stands out as the most appropriate and effective choice for treating Listeria monocytogenes infections.