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'') a ...

is 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/Hansen's disease. NTM can cause pulmona ...

are divided into four groups. The first three groups are classified as "Slowly growing Mycobacteria" and the fourth group as "Rapid Growers".

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 kansasii'' is a Bacteria, bacterium in the ''Mycobacterium'' genus. It is an environmental bacteria that causes opportunistic infections in humans, and is one of the leading mycobacterial causes of human disease after tuberculosi ...

'', ''

Mycobacterium intermedium ''Mycobacterium intermedium'' is a 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''. Etymology: Latin; int ...

'', ''

Mycobacterium marinum ''Mycobacterium marinum'' is a slow growing fresh and saltwater mycobacterium (SGM) belonging to the genus ''Mycobacterium'' and the phylum Actinobacteria. It was formerly known as ''Mycobacterium balnei''. The strain marinum was first identified ...

'', ''

Mycobacterium asiaticum ''Mycobacterium asiaticum'' is a slowly growing photochromogenic mycobacterium ''Mycobacterium'' is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to ...

'', and ''

Mycobacterium simiae ''Mycobacterium simiae'' 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 szulgai ''Mycobacterium szulgai'' is a species of ''Mycobacterium''. It is a scotochromogen Scotochromogenic bacteria develop pigment in the dark. Runyon Group II nontuberculous mycobacteria such as ''Mycobacterium gordonae ''Mycobacterium gordona ...

'' 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 (

scotochromogen Scotochromogenic bacteria develop pigment in the dark. Runyon Group II nontuberculous mycobacteria such as ''Mycobacterium gordonae ''Mycobacterium gordonae'' is a species of ''Mycobacterium'' named for Ruth E. Gordon. It is a species of th ...

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

'' and ''

Mycobacterium gordonae ''Mycobacterium gordonae'' is a species of ''Mycobacterium'' named for Ruth E. Gordon. It is a species of the phylum Actinomycetota (Gram-positive bacteria with high guanine and cytosine content, one of the dominant phyla of all bacteria), bel ...

'', among others. ''

'' 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 nontu ...

'' 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 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. ''

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 no ...

'' is also a nonchromogen.

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 diseas ...

'', ''

Mycobacterium abscessus ''Mycobacteroides abscessus'' (formerly ''Mycobacterium abscessus'') is a species of rapidly growing, multidrug-resistant, nontuberculous mycobacteria (NTM) that is a common soil and water contaminant. Although ''M. abscessus'' most commonly ca ...

'', ''

Mycobacterium chelonae ''Mycobacteroides chelonae'' (formerly ''Mycobacterium chelonae'') is a species of bacteria from the phylum Actinomycetota belonging to the genus '' Mycobacteroides''. ''Mycobacteroides chelonae'' is a rapidly growing mycobacterium that is found ...

'', ''

Mycobacterium thermoresistibile ''Mycobacterium thermoresistibile'' 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 ...

'', ''

Mycobacterium smegmatis ''Mycobacterium smegmatis'' is an acid-fast bacterium, bacterial species in the phylum ''Actinomycetota'' and the genus ''Mycobacterium''. It is 3.0 to 5.0 μm long with a bacillus (shape), bacillus shape and can be stained by Ziehl–Neels ...

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

References

*R {{Mycobacterium-stub