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