22 - Runyon classification (of Nontuberculous Mycobacteria)

The Runyon classification of nontuberculous mycobacteria based on the rate of growth, production of yellow pigment and whether this pigment was produced in the dark or only after exposure to light.

It was introduced by Ernest Runyon in 1959.

On these bases, the nontuberculous mycobacteria are divided into four groups:


SLOWLY GROWING MYCOBACTERIA :

The first three groups are classified as "Slowly growing Mycobacteria".

Runyon I: Photochromogens
Runyon I organisms (photochromogens) are slow growing, and produce a yellow-orange pigment when exposed to light. Mycobacterium kansasii, Mycobacterium marinum, Mycobacterium simiae, Mycobacterium asiaticum.

Runyon II: Scotochromogens
Runyon II organisms (scotochromogens) are slow growing, and produce a yellow-orange pigment in light or in the dark. Mycobacterium scrofulaceum, Mycobacterium gordonae, Mycobacterium szulgai, Mycobacterium xenopi, Mycobacterium celatum, Mycobacterium flavescens.


Runyon III: Nonchromogenic
Runyon III organisms are slow growing, and do not produce pigment. Mycobacterium avium-intracellulare, Mycobacterium xenopi, Mycobacterium terrae, Mycobacterium paratuberculosis, Mycobacterium shimoidae, Mycobacterium genavense


Runyon IV: RAPID GROWERS : 

Runyon IV organisms are rapid growing for mycobacteria (colonies in 5 days). They do not produce pigment. Mycobacterium fortuitum, Mycobacterium peregrinum, Mycobacterium abscessus, Mycobacterium chelonae,   Mycobacterium thermoresistibile,  Mycobacterium peregrinum .

Some rapidly growing mycobacteria are considered "late-pigmenting".