Home Contact Us

Non Tuberculous Mycobacteria (NTM) / MOTT - Characterstics, Classification, Morphology, MAC

Last Modified: July 19, 2022

Characteristics of Non Tuberculous Mycobacteria (NTM) / MOTT

Non-Tuberculous Mycobacteria (NTM) / MOTT includes all mycobacterial species that do not belong to Mycobacterium tuberculosis. Approximately 130 species of NTM are present in this group. Other names used to designate the NTM includes.

  • Anonymous

  • Atypical

  • Unclassified

  • Tuberculoid

  • Unknown

  • Environmental

  • Mycobacterial other than tubercle bacilli (MOTT)

  • opportunistic

Non-Tuberculous Mycobacteria (NTM) / MOTT are present everywhere in the environment and sometimes colonize the skin and respiratory and gastrointestinal tract of healthy individuals. Infection is acquired by mechanisms such as trauma, inhalation of infectious aerosols, ingestion, nosocomial, and an iatrogenic infection.

NTM is not transmitted from person to person. Its isolation does not necessarily mean disease association

Classification of Non Tuberculous Mycobacteria (NTM) / MOTT

Non Tuberculous Mycobacteria (NTM) / MOTT was classified by Runyon in 1959 into 4 groups on the basis of their phenotypic characteristics growth rate and colonial pigmentation.

* Runyon classification of NTM- slow-growing NTM:

Runyon group no. I

Group Name: Photochromogens

  • pigmentation disappears after reincubation in dark for 24-48 hours

  • It produces yellow-orange colonies

    Eg: Mycobacterium kansasii, Mycobacterium asiaticum, Mycobacterium marinum, Mycobacterium simiae, Mycobacterium intermedium

Description: Non-Tuberculous Mycobacteria (NTM) / MOTT colonies that develop pigment on exposure to light for 1 hour after being grown in the dark and take longer than 7 days to appear on solid media (slow grower)

Runyon group no. II

Group Name: Scotochromogens

  • colonies, pigmented either grown in dark or light

  • produce yellow, orange, or red pigmented colonies on LJ medium

    (photochromogenic at 25°C and scotochromogenic at 35°C)

    Eg: Mycobacterium szulgai, Mycobacterium interjectum, Mycobacterium scrofulaceum, Mycobacterium gordonae, Mycobacterium cooki, Mycobacterium hiberniae, Mycobacterium feavesceris

Description: Non-Tuberculous Mycobacteria (NTM) / MOTT colonies that develop pigment in the dark or light or light and take longer than 7 days to appear on solid media

Runyon group no. III

Group Name: Non-phagochromosomes

  • found mostly in the environment, soil, and water

  • produces a disease similar to pulmonary tuberculosis in patients with compromised pulmonary function, such as patients with chronic bronchitis or obstructive pulmonary disease

  • In patients with HIV, MAC (Mycobacterium avium complex) produces disseminated disease affecting every organ

    Eg: Mycobacterium ulcerans, Mycobacterium xenopi, M. haemophilum

Description: Non-Tuberculous Mycobacteria (NTM) / MOTT colonies that are non-pigmented regardless of whether they are grown in dark or light and take longer than 7 days to appear on solid media

Group Name: Rapid growers

  • causes disseminated cutaneous infection, chronic pulmonary infection, post-traumatic wound infection

    Eg: Mycobacterium chelonae, Mycobacterium mucogericum, Mycobacterium smegmatis, Mycobacterium fortuitum, Mycobacterium abscessus, Mycobacterium peregrinum

Description:

  • NTM colonies that grow on solid media (also routine bacterial media) and take fewer than 7 days to appear; present worldwide

  • this group may also include photochromogens, scotochromogens, non-photochromogens species

  • can be environmental, nosocomial, commensals in skin

  • they gain entry into the host by inoculation into the skin and subcutaneous tissue as a result of trauma, infections, surgery, or through animal contact

Morphology of Non Tuberculous Mycobacteria (NTM) / MOTT

Non-Tuberculous Mycobacteria (NTM) / MOTT produces colonies within 1-2 weeks of incubation in LJ media. They can grow at 25°C, 37 °C, and even at 44 °C. Some of them produce bright yellow or orange pigments during their growth on the LJ medium.

They are acid as well as alcohol faster, arylsulfatase test positive but are niacin and neutral red reactions negative, non-pathogenic for guinea pigs but pathogenic for the mouse.

They are usually resistant to antitubercular drugs such as streptomycin, isoniazid, and p-aminosalicylic acid.

Mycobacterium avium complex (MAC)

Mycobacterium avium complex comprises:

  • Mycobacterium avium

  • Mycobacterium vulneris

  • Mycobacterium intracellulare

  • Mycobacterium marseillense

  • Mycobacterium bouchedurbonense

  • Mycobacterium timonense

  • Mycobacterium avium subsp. avium

  • Mycobacterium avium subsp. paratuberculosis

  • Mycobacterium avium subsp. silvaticum (wood pegion bacillus)

Largely because of the increasing population of Immuno-suppressed patients, the incidence of infection caused by MAC has increased – mostly causing pulmonary infections.

They are among the most commonly isolated NTM species that have been isolated from natural water, soil, dairy products, pigs, chickens, cats, and dogs. Infection is acquired by inhalation or ingestion.

MAC and other Non-Tuberculous Mycobacteria (NTM) / MOTT have extraordinary starvation survival; can persist well over a year in tap water and tolerate extreme temperatures. Mycobacterium avium can infect, invade and replicate in protozoa, amoeba-grown Mycobacterium avium is more invasive toward human epithelial and macrophage cells.

MAC cultures can have an opaque, translucent, or transparent colony morphology. Transparent colonies are more virulent as they are more drug-resistant. Mycobacterium avium sub spp. paratuberculosis is known to cause inflammatory bowel disease (Johne's disease), and chronic inflammatory bowel disease (Crohn's disease).

They are extremely fastidious- require growth factor Mycobactin, produced by Mycobacteria species such as Mycobacterium phlei (a saprophytic strain). Primary isolation takes 6-18 months.

Immunocompromised individuals, such as AIDS patients cause disseminated disease. In patients without AIDS-pulmonary infection in patients with pre-existing pulmonary disease; cervical lymphadenitis.

Sorry!

We cannot find any articles on this URL.