This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
M. avium intracellulare is: September 2009 
Select and explain. 
A. Non photochromogens, B. Scotochromogens, C. Photochromogens, D. Rapid growers
A: Non photochromogens
Answer: A: Non photochromogens 
Explanation: Ans. A: Non photochromogens Runyon Groups * Pigmentation studies - Scotochromogens: Pigmentation in the dark (and light) - Photochromogens: Pigmentation only after exposure to light - Non-photochromogens: No pigment forms Group I: photochromogens - Mycobacterium kansasii - Mycobacterium marinum Group II: scotochromogens - Mycobacterium scrofulaceium - Mycobacterium gordonae Group III: non-photochromogens - Mycobacterium avium complex Group IV: Rapid growers - Mycobacterium fouitum - Mycobacterium chelonei