The Timpe and Runyon classification of nontuberculous

mycobacteria ''Mycobacterium'' is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis (''M. tuberculosis'') and ...

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 (NTM), also known as environmental mycobacteria, atypical mycobacteria and mycobacteria other than tuberculosis (MOTT), are mycobacteria which do not cause tuberculosis or leprosy (also known as Hansen's disease). NTM d ...

are divided into four groups:

Slowly growing Mycobacteria

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

Runyon I: Photochromogens

Runyon I organisms (

photochromogen Mycobacteria that form colonies clearly visible to the naked eye in more than 7 days on subculture are termed slow growers. They can cause disease in humans. List of slowly growing Mycobacteria Nonchromogenic Rough * Mycobacterium africanum ...

s) are slow growing, and produce a yellow-orange pigment when exposed to light. The group includes '' Mycobacterium kansasii'', ''

Mycobacterium marinum ''Mycobacterium marinum'' is a slow growing mycobacterium (SGM) belonging to the genus ''Mycobacterium'' and the phylum Actinobacteria. The strain marinum was first identified by Aronson in 1926 and it is observed as a pathogenic mycobacterium. F ...

'', ''

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 *Gram-positive, nonmotile, acid-fast, ...

'', and '' Mycobacterium simiae''. '' Mycobacterium szulgai'' is a photochromogen when grown at 24 degrees, and a scotochromogen at 37 degrees. In contrast, Runyon classifications III through IV are considered ''nonphotochromogens'', in that exposure to light does not make them produce pigment which they would not develop in dark growing conditions.

Runyon II: Scotochromogens

Runyon II organisms ( scotochromogens) are slow-growing and produce a yellow-orange pigment regardless of whether they are grown in the dark or the light. The group includes '' Mycobacterium gordonae'' and '' Mycobacterium scrofulaceum'', among others. '' Mycobacterium szulgai'' is a scotochromogen when grown at 37 degrees, as mentioned above.

Runyon III: Nonchromogens

Runyon III organisms (nonchromogens) are slow-growing and never produce pigment, regardless of culture conditions. The group includes ''

Mycobacterium avium ''Mycobacterium avium ''complex is a group of mycobacteria comprising ''Mycobacterium intracellulare'' and ''Mycobacterium avium'' that are commonly grouped because they infect humans together; this group, in turn, is part of the group of nontub ...

'' and ''

Mycobacterium intracellulare ''Mycobacterium'' is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis (''M. tuberculosis'') and ...

'' (together known as the MAC complex), '' Mycobacterium tuberculosis'', ''

Mycobacterium ulcerans ''Mycobacterium ulcerans'' is a species of bacteria found in various aquatic environments. The bacteria can infect humans and some other animals, causing persistent open wounds called Buruli ulcer. ''M. ulcerans'' is closely related to ''Mycoba ...

'' and numerous other organisms.

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'' is a nontuberculous species of the phylum Actinomycetota (Gram-positive bacteria with high guanine and cytosine content, one of the dominant phyla of all bacteria), belonging to the genus ''Mycobacterium''. Backgroun ...

'', ''

Mycobacterium peregrinum Mycobacterium peregrinum is a species of ''Mycobacterium ''Mycobacterium'' is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases i ...

'', '' Mycobacterium abscessus'', '' Mycobacterium chelonae'', '' Mycobacterium thermoresistibile''. Some rapidly growing mycobacteria are considered "late-pigmenting".

References

*R {{Mycobacterium-stub