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Environmental mycobacteria, also known as Non Tubercule Mycobacteria (NTM) and mycobacteria other than tuberculosis (MOTT) are widely distributed in the environment, particularly in wet soil, marshland, streams, rivers and estuaries. They belong to the same family as the organisms that cause tuberculosis and leprosy, but unlike those organisms, NTM vary greatly in their ability to cause disease, and are not spread from person to person.

Mycobacterial infections are notoriously difficult to treat due to the organism’s cell wall, which is neither truly Gram negative nor positive. All Mycobacterium species share a characteristic cell wall, thicker than in many other bacteria, which is hydrophobic, waxy, and rich in mycolic acids/mycolates. The cell wall makes a substantial contribution to the hardiness of these organisms enabling them to survive long exposure to acids, alkalis, detergents, oxidative bursts, lysis, heat and many antibiotics.

Environmental mycobacteria also have extraordinary starvation survival persisting despite low nutrient levels in tap water. Furthermore, tolerance of temperature extremes results in contamination of hot tap water, spas, and ice machines by environmental mycobacteria.

Regulatory Information

Due to their extreme resistance to thermal and chemical disinfection, environmental mycobacteria present a particular problem when they occur in final rinse water used to decontaminate medical devices. Standards and guidance, such as ISO 15883, HTM 2030 (withdrawn), HTM 01-06 (formerly CFPP 01-06) detail the requirements to analyse water samples for the presence of Environmental Mycobacteria.  Prior to the release of CFPP 01-06 the requirement was for annual testing. The requirement for Environmental Mycobacteria testing of Endoscopy Final Rinse Water is now Quarterly.

Analytical Methods

Normal growth media will not support the growth of Environmental Mycobacteria so a specific, supplemented growth agar is used to promote the organisms growth. Samples are incubated at 30°C for 28 days, but are checked every 7 days for presumptive growth. Presumptive colonies are confirmed as Environmental Mycobacteria by negative oxidase reaction and Ziehl-Neelsen staining. In accordance with HTM 01-06 (formerly CFPP 01-06) and ISO 15883-4 Annex, Environmental Mycobacterium must not be detected after 28 days incubation.  CFPP 01-06 increased the frequency of testing from annually, as stipulated in HTM2030, to quarterly.

Health Effects


Humans are exposed to environmental mycobacteria in water through drinking, swimming, and bathing. Aerosols generated during these activities can also lead to human exposure. The presence of environmental mycobacteria in water coupled with their resistance to disinfection leads to the presence of environmental mycobacteria in hot tubs, solutions used in medical treatment and water-oil emulsions used to cool metalworking tools. Dusts can be rich sources of environmental mycobacteria, especially dust rich in peat. Foodstuffs and cigarettes have also been documented as sources of mycobacterial infection.


The most common clinical manifestation of NTM disease is lung disease, but lymphatic, skin/soft tissue and disseminated disease are also caused by the organisms. Rapidly growing NTMs are implicated in catheter infections, post-LASIK, skin and soft tissue (especially post-cosmetic surgery) and pulmonary infections.


The treatment of environmental mycobacterial infections is almost always more complicated than the treatment of tuberculosis. The drugs, frequency of administration, and duration of therapy will vary depending on the species of NTM causing the disease, the site of infection and the extent of disease.

Although some anti-tuberculous drugs are also active against NTM, treatment of most infections also requires antibiotics that are not typically used to treat tuberculosis. The treatment may depend on laboratory tests of antibiotic resistance of the isolate causing the disease and prolonged courses of intravenous or inhaled antibiotic therapy may be required.

The prognosis for pulmonary infections due to environmental mycobacteria is variable and depends on many factors including the specific species involved and its drug susceptibility, the extent of disease, the presence of other medical problems and whether or not the patient can tolerate the treatment regimen.

Risk Factors

Whilst anyone can develop a mycobacterial infection, most patients have underlying structural lung disease such as chronic obstructive pulmonary disease (COPD), cystic fibrosis, bronchiectasis, prior tuberculosis or chronic aspiration. It is now known that immunosuppressive medications such as chemotherapy, prednisone or drugs used to treat conditions such as Rheumatoid Arthritis, psoriasis and Crohn’s Disease may increase the risk of NTM infection.

Prevention and Control

An effective strategy for preventing pulmonary NTM infections is lacking.

Although anti-tuberculous drugs have been used widely to prevent the development of tuberculosis there is no vaccine available for the prevention of environmental mycobacterial infections. There are, however, several reports that the vaccine for tuberculosis, Bacille Calmette-Guerin (BCG) offering some protection against NTM infection in children.

Prevention of health care related NTM infections requires that surgical wounds, injection sites, and intravenous catheters not be exposed to potable water or fluids derived from potable water. Endoscopes cleaned using potable water and clinical specimens contaminated with tap water or ice are also not acceptable and it is for this reason that regular surveillance of water used in the disinfection of medical devices for the presence of environmental bacteria is performed.

Should environmental mycobacteria contamination be found, control of the organism and rectification of the contamination can be extremely diifcult due to the organisms resistance to chemical disinfectants and tolerance of heat. Often multiple decontamination cycles using strong chemical disinfectants are required. Prevention of contamination through a multi pronged approach is considered more effective than treatment.

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