Runyon classification

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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. [1]


It was introduced by Ernest Runyon in 1959. [2]

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

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. NTM do cause pulmonary diseases that resemble tuberculosis. Mycobacteriosis is any of these illnesses, usually meant to exclude tuberculosis. They occur in many animals, including humans.

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. The group includes Mycobacterium kansasii, Mycobacterium marinum, Mycobacterium asiaticum, 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. [3]

<i>Mycobacterium kansasii</i> species of prokaryote

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 is a free-living bacterium, which causes opportunistic infections in humans. M. marinum sometimes causes a rare disease known as aquarium granuloma, which typically affects individuals who work with fish or keep home aquariums.

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

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.

Mycobacterium gordonae is a species of Mycobacterium named for Ruth E. Gordon. It is a species of the phylum actinobacteria, belonging to the genus Mycobacterium.

Mycobacterium scrofulaceum is a species of Mycobacterium.

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

Runyon III: Nonchromogens

Runyon III organisms (nonchromogens) are slow-growing and never produce pigment, regardless of culture conditions. The group includes Mycobacterium avium and Mycobacterium intracellulare (together known as the MAI complex), Mycobacterium ulcerans and numerous other organisms.

<i>Mycobacterium ulcerans</i> species of prokaryote

Mycobacterium ulcerans is a slow-growing mycobacterium that classically infects the skin and subcutaneous tissues, giving rise to indolent nonulcerated and ulcerated lesions. After tuberculosis and leprosy, Buruli ulcer is the third most common mycobacteriosis of humans. M. ulcerans grows optimally on routine mycobacteriologic media at 33 °C and elaborates a necrotizing immunosuppressive cytotoxin (mycolactone). The bacteria are considered microaerophilic. Large ulcers almost certainly caused by M. ulcerans were first observed by Cook in Uganda in 1897; however, the etiologic agent was not isolated and characterized until 1948 in Australia by MacCallum and associates.

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

<i>Mycobacterium fortuitum</i> species of prokaryote

Mycobacterium fortuitum is a nontuberculous species of the phylum Actinobacteria, belonging to the genus Mycobacterium.

Mycobacterium peregrinum is a species of Mycobacterium.

<i>Mycobacterium abscessus</i> species of prokaryote

Mycobacterium abscessus complex (MABSC) is a group of rapidly growing, multidrug-resistant non-tuberculous mycobacteria (NTM) species that are common soil and water contaminants. Although M. abscessus complex most commonly cause chronic lung infection and skin and soft tissue infection (SSTI), the complex can also cause infection in almost all human organs, mostly in patients with suppressed immune systems. Amongst NTM species responsible for disease, infection caused by M. abscessus complex are more difficult to treat due to antimicrobial drug resistance.

Some rapidly growing mycobacteria are considered "late-pigmenting". [4]

Related Research Articles

Scotochromogenic bacteria develop pigment in the dark. Runyon Group II nontuberculous mycobacteria are examples but the term could apply to many other organisms.

Mycobacterium botniense is a slowly growing Mycobacterium, which produces a yellow pigment. It was first isolated from a stream of water. M. botniense is most closely related to Mycobacterium xenopi. Etymology: botniense; of Botnia, referring to the Latin name of the province of Finland from which the isolation was made.

<i>Mycobacterium chelonae</i> species of prokaryote

Mycobacterium chelonae is a species of the phylum Actinobacteria, belonging to the genus Mycobacterium. 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.

Mycobacterium elephantis, a bacterium of the family Mycobacteriaceae, was discovered and isolated from a deceased elephant near India and may be linked to respiratory dysfunction. Organisms in the genus Mycobacterium are known to be aerobic and non-motile. Organisms within Mycobacterium belong to either the rapid growing group or the slow growing group. M. elephantis is classified as a rapid grower and relates most closely to Mycobacterium confluentis and Mycobacterium phlei.

Mycobacterium flavescens is a species of the phylum Actinobacteria, belonging to the genus Mycobacterium.

Mycobacterium gadium is a species of the phylum Actinobacteria, belonging to the genus Mycobacterium.

Mycobacterium hassiacum is a rapid-growing thermophilic mycobacterium that was isolated in human urine in 1997 by researchers at the German University of Regensburg. It's a species of the phylum Actinobacteria, belonging to the genus Mycobacterium.

Mycobacterium avium complex is a group of mycobacteria comprising Mycobacterium intracellulare and Mycobacterium avium that are commonly grouped together because they infect humans together; this group, in turn, is part of the group of nontuberculous mycobacteria. These bacteria cause disease in humans called Mycobacterium avium-intracellulare infection or Mycobacterium avium complex infection.

Mycobacterium tusciae is a slow-growing, scotochromogenic mycobacterium first isolated from a lymph node of an immunocompromised child and subsequently from tap water and from a respiratory specimen of a patient with chronic fibrosis. Etymology: tusciae referring to the Italian region of Tuscany, where the organisms were first isolated.

In microbiology, the phenotypic testing of mycobacteria uses a number of methods. The most-commonly used phenotypic tests to identify and distinguish Mycobacterium strains and species from each other are described below.

Rapid growing mycobacterium consists of organism of the Mycobacterium fortuitum group and Mycobacterium chelonae/Mycobacterium abscessus group and these usually cause subcutaneous abscesses or cellulitis following trauma in immunocompetent patients.

The MCAG group is a group of Mycobacteria.

Mycobacterium terrae is a slow-growing species of Mycobacterium. It is an ungrouped member of the third Runyon. It is known to cause serious skin infections, which are "relatively resistant to antibiotic therapy".

Mycobacterium simiae is a species of Mycobacterium.As per Runyon's classification it is classified as a photochromogen as it produces pigments only when exposed to light.


  1. Rogall T, Wolters J, Flohr T, Böttger EC (October 1990). "Towards a phylogeny and definition of species at the molecular level within the genus Mycobacterium". International Journal of Systematic Bacteriology. 40 (4): 323–30. doi:10.1099/00207713-40-4-323. PMID   2275850.
  2. Runyon EH (January 1959). "Anonymous mycobacteria in pulmonary disease". The Medical clinics of North America. 43 (1): 273–90. PMID   13612432.
  3. Koneman, Elmer W. (1988). Color atlas and textbook of diagnostic microbiology. Philadelphia: Lippincott Williams & Wilkins. p. 560. ISBN   9780397508259. Runyon has termed these organisms nonphotochromogenic, meaning that exposure to light does not make the[ir] pigment more intense.
  4. Brown-Elliott BA, Wallace RJ (October 2002). "Clinical and taxonomic status of pathogenic nonpigmented or late-pigmenting rapidly growing mycobacteria". Clin. Microbiol. Rev. 15 (4): 716–46. doi:10.1128/cmr.15.4.716-746.2002. PMC   126856 Lock-green.svg. PMID   12364376.