What are the hallmark features and typical risk groups for Listeria monocytogenes infection?

• A. Meningitis in healthy adults only
• B. Flu-like illness or gastroenteritis; high risk in pregnant women, neonates, elderly, and immunocompromised; can cause meningitis and fetal infection
• C. Severe pneumonia in smokers
• D. Acute hemorrhagic diarrhea in travelers

Answer: (B)

Listeria infection is notable for a wide clinical range: most people who ingest it develop only a mild illness such as flu-like symptoms or gastroenteritis, but certain groups are highly vulnerable to invasive disease. Pregnant women, their fetuses and neonates, the elderly, and immunocompromised individuals are at the greatest risk because the bacteria can invade the bloodstream and the central nervous system, and it can cross the placenta to infect the fetus. This combination—common, mild illness in the general population with a real threat of severe invasive disease including meningitis and fetal infection in high-risk groups—best matches the described scenario.

The other patterns don’t fit Listeria well. It isn’t confined to meningitis in healthy adults, it doesn’t typically cause severe pneumonia in smokers as a hallmark, and it is not typically associated with acute hemorrhagic diarrhea in travelers.