How long does Mycobacterium fortuitum take to grow on MacConkey agar?

How long does Mycobacterium fortuitum take to grow on MacConkey agar?

• A. 2 days
• B. 3 days
• C. 5 days
• D. 7 days

Answer: (C)

Rapid-growing mycobacteria like Mycobacterium fortuitum tend to form colonies on MacConkey agar within a few days. Because this organism is a rapid grower, colonies are typically visible after about five days of incubation at 35–37°C. While some strains may appear a bit earlier, five days is the standard timeframe used in labs and exams for this species. In contrast, slow-growing mycobacteria, such as M. tuberculosis, require weeks to grow, which highlights the distinction in growth rates. Therefore, five days best fits the expected growth window.

Rapid-growing mycobacteria like Mycobacterium fortuitum tend to form colonies on MacConkey agar within a few days. Because this organism is a rapid grower, colonies are typically visible after about five days of incubation at 35–37°C. While some strains may appear a bit earlier, five days is the standard timeframe used in labs and exams for this species. In contrast, slow-growing mycobacteria, such as M. tuberculosis, require weeks to grow, which highlights the distinction in growth rates. Therefore, five days best fits the expected growth window.