Growth on buffered charcoal yeast extract (BCYE) agar for Legionella pneumophila may not be visible for how long?

Growth on buffered charcoal yeast extract (BCYE) agar for Legionella pneumophila may not be visible for how long?

• A. 1 day
• B. 2-3 days
• C. 3-4 days
• D. 5-6 days

Answer: (C)

Legionella pneumophila grows slowly on charcoal yeast extract–based media, so colonies don’t appear right away. On BCYE, you typically start to see colonies after about three to four days of incubation. Shorter incubations (one to two days) are usually too early to detect it, while waiting longer than four days isn’t necessary for routine detection, though some very slow cases or low inocula may show growth a bit later. So the window when growth may not yet be visible is three to four days.

Legionella pneumophila grows slowly on charcoal yeast extract–based media, so colonies don’t appear right away. On BCYE, you typically start to see colonies after about three to four days of incubation. Shorter incubations (one to two days) are usually too early to detect it, while waiting longer than four days isn’t necessary for routine detection, though some very slow cases or low inocula may show growth a bit later. So the window when growth may not yet be visible is three to four days.