Which organism is classified as a photochromogen?

The classification of organisms as photochromogens is based on their ability to produce pigment in the presence of light. In the case of Mycobacterium kansasii, this organism is known to produce a yellow-orange pigment when exposed to light, which is a characteristic feature of photochromogens. This pigment production is not observed in the dark, distinguishing photochromogens from other types of mycobacteria.

In contrast, other species mentioned have different properties. Mycobacterium avium, for instance, does not produce pigments either in the light or in the dark and is classified differently. Mycobacterium gordonae can produce pigment but is categorized as a scotochromogen, as it produces pigment in both light and dark conditions. Mycobacterium chelonei, on the other hand, does not exhibit the pigment-producing characteristics associated with photochromogens either. Understanding these characteristics helps in the identification and classification of mycobacterial species in clinical microbiology.