Ampicillin coverage is included in empiric meningitis therapy to cover Listeria in which populations?

• A. Children under 2 years old.
• B. Pregnant women.
• C. Healthy adults under 40.
• D. Patients aged 50 years or older or those who are immunocompromised.

Answer: (D)

Listeria meningitis is more likely in people with weaker cell-mediated immunity, such as older adults and those who are immunocompromised. Ampicillin is added to empiric meningitis regimens specifically to cover Listeria because cephalosporins, which are often used as part of the initial therapy, do not reliably cover Listeria. Therefore, in patients aged 50 years or older or who are immunocompromised, including ampicillin ensures Listeria is treated if present, while the rest of the regimen covers the common meningitis pathogens like Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae.

The other groups—younger children (neonates) and healthy adults under 40—do not have the same elevated risk for Listeria in the context of adult meningitis, so ampicillin is not routinely added for them. Pregnant women have Listeria risk in general, but the standard at-risk category used for adjusting empiric meningitis therapy in adults centers on age 50+ or immunocompromise.