Which of the following is characteristic of Mycobacterium kansasii?

• A. Rapid growing
• B. Nonchromogenic
• C. Considered a laboratory contaminant
• D. Infections usually acquired by respiratory route

Answer: (D)

Infections with Mycobacterium kansasii are typically acquired through the respiratory route, leading to pulmonary disease. This organism is a slow-growing, photochromogenic non-tuberculous mycobacterium, which means it takes weeks to form colonies in culture and develops pigment (usually yellow) when exposed to light. It is not considered a laboratory contaminant; it behaves as a true pathogen, especially in people with underlying lung disease. The statement that fits best is that infections are usually acquired by the respiratory route because that mirrors how the organism is encountered in the environment and how disease presents clinically. The other descriptions don’t fit: it’s not rapid-growing, it is chromogenic (not nonchromogenic), and it is not typically a contaminant.