Mycobacteria are a diverse group of rod-shaped bacteria that include more than 70 different species. Except for Mycobacterium tuberculosis (which causes the disease tuberculosis (TB)), and Mycobacterium leprae (which causes leprosy), most mycobacteria live in the soil and water in both rural and urban settings throughout the world. They can be found in aerosols, rivers and swamps, in treated water, public swimming pools, hot spas, humidifiers, aquariums, garden soils, food, and many other places. Because they are protected by their waxy lipid-rich cell wall, mycobacteria are resistant to disinfectants and water treatment measures.
There is not a standard naming convention for this group of microorganisms. They may be referred to as nontuberculous mycobacteria (NTM), mycobacteria other than tuberculosis (MOTT), atypical mycobacteria, and/or environmental mycobacteria. The term MOTT is still often used but is an older designation. “Nontuberculous mycobacteria” has come into use more recently so, for the purpose of this article, this group will be referred to as NTM.
Almost half of the NTM species identified are associated with opportunistic infections in animals and humans, and several have caused sporadic outbreaks. NTM are acquired through environmental exposure to water, aerosols, soil, and dust – through inhalation, ingestion, and through breaks in the skin due to injuries, surgical procedures, or IV catheters.
Anyone can become infected, but people with suppressed immune systems (such as AIDS patients and transplant recipients), people with pre-existing lung damage (such as from smoking and previous tuberculosis) and those with lung diseases (such as emphysema or cystic fibrosis) are most likely to be affected. NTM infections can be challenging and time-consuming to treat since the organisms may be resistant to commonly prescribed antibiotics.