What are nontuberculous mycobacteria?
Nontuberculous mycobacteria (NTM) are a diverse group of bacteria that include more than 150 different species, some of which can infect and cause illness in humans. The term nontuberculous mycobacteria refers to all the species in the family of mycobacteria that may cause human disease but that do not cause tuberculosis (TB). Photo source for M. fortuitum: CDC, Margaret Williams and Janice Haney Carr
These bacteria are common throughout the world, thriving in soil and water – including rivers and swamps, treated drinking water, swimming pools, hot tubs, humidifiers, aquariums/fish tanks, and garden soils – in both rural and urban settings. Significantly, NTM often contaminate the water supplies of hospitals and other medical facilities. Because they are protected by their waxy, fatty (lipid-rich) cell walls, NTM are resistant to usual disinfectants, water treatment measures, and antibiotics.
Almost half of the nontuberculous mycobacteria species identified are associated with opportunistic infections in animals and humans, and several have caused periodic outbreaks. The exact ways in which NTM enter a person has not been identified, but inhaling contaminated air or water droplets, drinking contaminated water, and direct contact with NTM through breaks in the skin or the accidental use of contaminated medical equipment (catheters, endoscopes, bronchoscopes) are considered the most likely routes of exposure. Unlike M. tuberculosis, the organism that causes tuberculosis, NTM are not passed from person to person (or animal to human).
Because NTM exist in the environment, nearly everyone will be exposed to some of these organisms, but most will not develop clinical signs of infection. For reasons that are not fully understood, people with weakened immune systems, such as those with AIDS and transplant recipients, people with pre-existing lung damage from smoking or previous tuberculosis, for example, and people with lung diseases such as emphysema, COPD, or cystic fibrosis are prone to NTM infections.
Most often, NTM infections develop in the lungs and can lead to severe lung disease in some individuals. NTM infections also occur in the lymph nodes, bones, skin, and soft tissues. NTM infections may be limited (localized) to one part of the body or they may spread (disseminate) throughout the body. NTM infections can be challenging and time-consuming to treat since the organisms may be resistant to commonly prescribed antibiotics.