Which organism is a Gram-positive rod known to cause meningitis in neonates and immunocompromised adults and can grow at refrigeration temperatures?

• A. Listeria monocytogenes
• B. Streptococcus pneumoniae
• C. Staphylococcus aureus
• D. Bacillus cereus

Answer: (A)

Listeria monocytogenes is a Gram-positive rod that is notable for its ability to grow at refrigerator temperatures, a rare trait among meningitis-causing organisms. This cold tolerance means it can multiply in refrigerated foods, leading to exposure through consumption of contaminated dairy products and meats. In people who are pregnant, immunocompromised, or very young, Listeria can invade the body, cross the blood–brain barrier, and cause meningitis. This combination of being a Gram-positive rod, causing meningitis in neonates and immunocompromised adults, and its ability to grow at low temperatures makes Listeria monocytogenes the best answer.