Legionella pneumophila is best cultured on which medium?

• A. Blood agar
• B. MacConkey agar
• C. Chocolate agar
• D. Buffered charcoal yeast extract agar

Answer: (D)

Legionella pneumophila is a fastidious organism that needs nutrients not provided by routine culture media. It requires cysteine and iron and a medium that can neutralize harmful substances produced in culture. Buffered charcoal yeast extract agar provides these essentials: the charcoal helps detoxify the environment and supports a large surface area for growth, yeast extract supplies basic growth factors, the medium is buffered to maintain a stable pH, and cysteine and iron supplements meet the organism’s specific requirements. Because of these needs, it doesn’t grow well on standard media like blood agar or MacConkey, making buffered charcoal yeast extract agar the best choice for culturing Legionella pneumophila.