What are nontuberculous mycobacteria?
Mycobacteria are a diverse group of rod-shaped bacteria that include more than 100 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 city 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. Unlike M. tuberculosis, they are not passed from person-to-person with the exception of M. leprae, which requires extended close contact, such as with an infected family member. NTM can cause lung infections, bronchiectasis, lymph node infections, bone infections, abscesses, and skin and soft tissue infections, which may be localized or disseminated throughout the body. M. leprae can cause peripheral nerve damage and skin lesions. Most NTM reproduce slowly, which allows the infection to emerge weeks, months, or even years after the initial exposure.
Anyone can become infected, but people with suppressed immune systems (such as those with HIV/AIDS and transplant recipients), people with pre-existing lung damage (such as from smoking and previous tuberculosis) and those with lung diseases (such as emphysema, COPD, or cystic fibrosis and bronchiectasis) 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.