Which medium is used to identify Legionella in the lab?

Which medium is used to identify Legionella in the lab?

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

Answer: (A)

Legionella is a fastidious organism that doesn’t grow well on routine culture media, so it requires a specialized medium to isolate it. Buffered charcoal yeast extract agar provides the right combination of nutrients and environmental conditions—charcoal to detoxify toxins, yeast extract for nourishment, and buffering, often with additives like cysteine and iron—that Legionella needs to grow. Because of this, it is the standard medium used to identify Legionella from clinical specimens. The other media listed are not suitable for Legionella isolation: MacConkey agar targets many Gram-negative enterics and isn’t supportive for Legionella; blood agar is a general-purpose medium that doesn’t favor Legionella growth; Sabouraud dextrose agar is designed for fungi, not bacteria.

Legionella is a fastidious organism that doesn’t grow well on routine culture media, so it requires a specialized medium to isolate it. Buffered charcoal yeast extract agar provides the right combination of nutrients and environmental conditions—charcoal to detoxify toxins, yeast extract for nourishment, and buffering, often with additives like cysteine and iron—that Legionella needs to grow. Because of this, it is the standard medium used to identify Legionella from clinical specimens.

The other media listed are not suitable for Legionella isolation: MacConkey agar targets many Gram-negative enterics and isn’t supportive for Legionella; blood agar is a general-purpose medium that doesn’t favor Legionella growth; Sabouraud dextrose agar is designed for fungi, not bacteria.