Which of the following is not characteristic of Mycobacterium kansasii?

• A. Nonchromogenic
• B. Slow growing
• C. Obligate aerobe
• D. Infections usually acquired by respiratory route

Answer: (A)

Mycobacterium kansasii is a slow-growing, photochromogenic mycobacterium that commonly causes a pulmonary disease resembling tuberculosis. It is an obligate aerobe and infections are typically acquired by the respiratory route, through inhalation of environmental mycobacteria. The pigment trait is a key identifying feature: it produces pigment when exposed to light, so colonies become yellow to orange after light exposure. Because of this, labeling it as nonchromogenic would be incorrect. In the lab, you’d expect slow growth on media like Löwenstein–Jensen, with pigment development under light, which helps distinguish it from nonpigmented, nonchromogenic species.