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Medical Term:

Runyon classification

Pronunciation: run'yon

Definition: a classification scheme for mycobacteria other than Mycobacterium tuberculosis that divides species into four categories: photochromogens, species that produce a yellow to brown carotene pigment when grown in the presence of light; scotochromogens, which produce pigment in presence or absence of light; nonpigmented, which do not produce pigment; and rapid growers, which grow on solid media in 5–10 days rather than 4–8 weeks. This classification has no clinical or genetic significance but does remain of limited value in identification of some clinical isolates.

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