Which Mycobacterium species produces pigmented colonies in the dark (is a scotochromogen)?

Which Mycobacterium species produces pigmented colonies in the dark (is a scotochromogen)?

• A. M. szulgai
• B. M. kansasii
• C. M. tuberculosis
• D. All of these options

Answer: (A)

Mycobacterium szulgai is recognized for producing pigmented colonies even in the absence of light, classifying it as a scotochromogen. Scotochromogens are characterized by their ability to produce pigment when grown in the dark, as opposed to photochromogens which only produce pigment when exposed to light. This distinctive feature is crucial for identifying and differentiating Mycobacterium species in laboratory settings. Mycobacterium kansasii, while it does produce pigment, typically requires light to do so, categorizing it instead as a photochromogen. Mycobacterium tuberculosis is known for its pathogenicity but does not produce any pigment, making it neither a scotochromogen nor a photochromogen. The option indicating "All of these options" includes species that do not meet the criteria of being scotochromogens, further validating that Mycobacterium szulgai is the only correct choice in this context.

Mycobacterium szulgai is recognized for producing pigmented colonies even in the absence of light, classifying it as a scotochromogen. Scotochromogens are characterized by their ability to produce pigment when grown in the dark, as opposed to photochromogens which only produce pigment when exposed to light. This distinctive feature is crucial for identifying and differentiating Mycobacterium species in laboratory settings.

Mycobacterium kansasii, while it does produce pigment, typically requires light to do so, categorizing it instead as a photochromogen. Mycobacterium tuberculosis is known for its pathogenicity but does not produce any pigment, making it neither a scotochromogen nor a photochromogen. The option indicating "All of these options" includes species that do not meet the criteria of being scotochromogens, further validating that Mycobacterium szulgai is the only correct choice in this context.