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

Nontuberculous mycobacteria

Nontuberculous mycobacteria , also known as environmental mycobacteria, atypical mycobacteria and mycobacteria other than tuberculosis , are mycobacteria which do not cause tuberculosis or Hansen's disease ....

 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 kansasii

Mycobacterium kansasii is a bacterium in the Mycobacterium family. The genus includes species known to cause serious diseases in mammals, including tuberculosis and leprosy, but this species is generally not dangerous to healthy people....

, Mycobacterium marinum

Mycobacterium marinum

Mycobacterium marinum is a free-living bacterium, which causes opportunistic infections in humans.- History :Although Aronson isolated this mycobacterium in 1926 from a fish, it was not until 1951 that it was found to be the cause of human disease by Linell and Norden...

, Mycobacterium asiaticum

Mycobacterium asiaticum

Mycobacterium asiaticum is a slowly growing photochromogenic mycobacterium first isolated from monkeys in 1965. M. asiaticum can, but rarely, causes human pulmonary disease.-Description:Microscopy...

Runyon II: Scotochromogens

Runyon II organisms (scotochromogens) are slow growing, and produce a yellow-orange pigment in light or in the dark. Some become darker with exposure to light.
Mycobacterium scrofulaceum

Mycobacterium scrofulaceum

Mycobacterium scrofulaceum is a species of Mycobacterium.It is the most common cause of cervical lymphadenitis in children.It is sometimes included in the "MAIS group" with Mycobacterium avium and Mycobacterium intracellulare....

, Mycobacterium gordonae

Mycobacterium gordonae

Mycobacterium gordonae is a species of Mycobacterium named for Ruth E. Gordon.-Description:Gram-positive, nonmotile and moderate to long acid-fast rods....

, Mycobacterium szulgai

Mycobacterium szulgai

Mycobacterium szulgai is a species of Mycobacterium. It is a Scotochromogen and is currently ungrouped. It is known to cause skin infections....

, Mycobacterium xenopi

Mycobacterium xenopi

Mycobacterium xenopi is a slow-growing scotochromogenic species of Mycobacterium. It was first reported by Schwabacher in 1959, having been isolated in lesions found on a Xenopus laevis, but the possibility of human infection was not confirmed until 1965.It has low pathogenicity in humans, and...

, Mycobacterium celatum

Mycobacterium celatum

Mycobacterium celatum is a mycobacterium.Type strain: strain ATCC 51131 = CCUG 39185 = CDC 90-0899 = CIP 106109 = DSM 44243 = JCM 12373.-References:...

, Mycobacterium flavescens

Mycobacterium flavescens

Mycobacterium flavescensEtymology: Latin, flavescens = becoming golden yellow.-Description:Gram-positive, nonmotile and acid-fast rods.Colony characteristics*Soft, yellow-orange scotochromogenic, butyrous colonies.Physiology...

Runyon III: Nonchromogenic

Runyon III organisms are slow growing, and do not produce pigment. Note that some may produce very pale yellow, buff, or tan pigment but do not intensify upon light exposure.
Mycobacterium avium-intracellulare, Mycobacterium terrae

Mycobacterium terrae

Mycobacterium terrae is a slow-growing species of Mycobacterium. It is an ungrouped member of the third Runyon...

, Mycobacterium paratuberculosis, Mycobacterium shimoidae, Mycobacterium genavense

Mycobacterium genavense

-Description:A slow-growing subspecies of Mycobacterium.Nonmotile, acid-fast coccobacilli . No formation of spores, capsules or aerial hyphae.Colony characteristics...

Runyon IV: Rapid Growers

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

Mycobacterium fortuitum

Mycobacterium fortuitum is a nontuberculous mycobacterium.-Background:Mycobacterium fortuitum is a fast-growing species that can cause infections. The term "fast growing" is a reference to a growth rate of 3 or 4 days, when compared to other Mycobacteria that may take weeks to grow out on...

, Mycobacterium peregrinum, Mycobacterium abscessus

Mycobacterium abscessus

Mycobacterium abscessus is a rapidly growing mycobacterium that is a common water contaminant. It was until recently thought to be a subspecies of Mycobacterium chelonae. M...

, Mycobacterium chelonae

Mycobacterium chelonae

Mycobacterium chelonae is a rapidly growing mycobacterium, that is found all throughout the environment including sewage and tap water. It can occasionally cause opportunistic infections of humans.It is grouped in Runyon group IV....

, Mycobacterium thermoresistible

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