Non-Tuberculous Mycobacteria – a 21st Century Waterborne Pathogen

Non-Tuberculous Mycobacteria (NTM) are microorganisms which can be found everywhere in our environment, not just in water but in soil, vegetation, aerosols and dust particles.  There are over 170 NTM species identified, although not all are clinically relevant, and this number is still increasing. 

The widespread introduction of disinfectants within drinking water treatment processes and distribution networks has created a selective environment in which the NTM family, with their protective and lipid-rich cell walls, can comfortably thrive.  The incidence of NTM disease has been steadily rising and whilst mainly considered to be a risk for those with significant lung problems and co-morbidities, it is clear that seemingly immune-competent individuals can be affected.

Non-Tuberculous Mycobacteria – A Difficult Adversary

NTM infections are tricky to diagnose, difficult to treat, the organisms are extremely antibiotic resistant, tolerant of temperatures, disinfectants, desiccation, salt concentrations, low oxygen levels and can readily adapt to and colonise new substrates.  Prevention to exposure remains the most effective step to safeguard those at known risk. 

Clinically the lung is most commonly affected, where pulmonary mycobacteriosis may be found in those individuals with predisposing conditions such as cystic fibrosis, chronic obstructive pulmonary disease and asthma, plus individuals with immune deficiency (genetic or drug-induced).  There is also a recognised group with pulmonary Mycobacterium avium complex (MAC) infection which represent elderly, white, post-menopausal females of slender build who continuously suppress a cough – described as “Lady Windemere Syndrome.”  A recognised condition of hypersensitivity pneumonitis – also known as Hot Tub Lung – is attributed to NTM.  This appears as an immune hypersensitivity response with chronic respiratory symptoms rather than a primary infection.  In addition to lung problems, NTM can also cause skin and soft tissue infections which manifest as lesions following tattoo procedures and cosmetic surgery for example, tenosynovitis (inflammation of the tendon sheath, usually in the fingers or wrist) and abscesses.

Seek Support from Molecular Diagnostic Techniques

NTM species can be split into “slow” or “rapid” growers based on plate culture techniques – however “rapid” is rather misleading as the organisms typically still take a week to grow if culturable.  “Slow” growers could keep you waiting much longer!  Ideally molecular techniques would be used to confirm a result and in a shorter period of time, particularly important as most human infections are caused by the slow growing Mycobacterium avium complex (MAC). 

The MAC includes subspecies silvaticumhominissuis and paratuberculosis, plus Mycobacterium intracellulare, Mycobacterium arosiense, Mycobacterium chimaera, Mycobacterium columbiense, Mycobacterium marseillense, Mycobacterium timonense, Mycobacterium bouchedurhonense, and Mycobacterium ituriense.  Mycobacterium chimaera‘s notoriety was heightened via contaminated water pipes and heater/cooler devices in cardiac surgery where subsequent investigative work raised the importance of qPCR for both recovery and identification of M. chimaera from the water samples taken (Zoccola, 2021).  Other NTM of note include Mycobacterium xenopi, Mycobacterium fortuitum complex, Mycobacterium kansasii, and the rapidly growing Mycobacterium abscessus group (MABS).

Focus for Risk Assessment and Environmental Surveillance

The presence of NTM in showerheads is well known, and also been shown to be the strongest predictor for infection (Tzou, 2020).  In healthcare facilities showerheads must be considered in a risk assessment and as a site for environmental surveillance regarding NTM.  Construction projects have been linked to outbreaks, most likely through contaminated dust particulates and/or release of biofilm within water pipework.  Other known problem sites include ice and water dispensers from fridges, hot tubs, spa baths, wet tested equipment and fittings (particularly those tested with chlorinated/controlled water sources).  MAC is 1000 times more resistant to chlorine than Escherichia coli, has a wide temperature range for growth and activity, therefore wet tested items may be a site of concern and for further investigation.  Control in the outbreak, or pseudo-outbreak situation, can be achieved via sterile water for consumption and relevant procedures.

Gundacker and co-workers (2022) from Wisconsin have recently published a case study of  Hot Tub Lung.  The individual involved had predisposing health factors and regularly used a hot tub.  Persistent respiratory symptoms were experienced, with diffuse lung infiltrates on X-ray/CT scan.  MAC was found in lung tissue and secretions.  The hypersensitivity pneumonitis reaction followed exposure to aerosolised hot tub water containing NTM.  After a protracted diagnostic pathway which ruled out other diseases, the individual stopped using the hot tub and underwent a long period of steroid treatment.  There was a marked improvement 2 months later and radiologic improvements after 6 months of treatment.

If non-tuberculous mycobacteria are not already on your radar as a member of a Healthcare Water Safety Team, or perhaps you are a hot tub owner, please consider recently published information and take precautionary steps and informed choices as appropriate.  Recognition of risk and implementation of water management plans may be vital for infection prevention . 

For more information, support, and guidance, please contact our team for a more informed discussion at

Kaul CM, Chan J, Phillips MS. Mitigation of nontuberculous mycobacteria in hospital water: challenges for infection prevention. Curr Opin Infect Dis. 2022 Aug 1;35(4):330-338

Pavlik I, Ulmann V, Falkinham JO 3rd. Nontuberculous Mycobacteria: Ecology and Impact on Animal and Human Health. Microorganisms. 2022 Jul 27;10(8):1516

 Gundacker ND, Gonzalez JA, Sheinin YM, Hirschtritt T. Hot Tub Lung: Case Report and Review of the Literature. WMJ. 2022 Jul;121(2):E31-E33. PMID: 35857699

Tzou, C.L.; Dirac, M.A.; Becker, A.L.; Beck, N.K.; Weigel, K.M.; Meschke, J.S.; Cangelosi, G.A. Association between Mycobacterium avium complex pulmonary disease and mycobacteria in home water and soil. Ann. Am. Thorac. Soc. 2020, 17, 57–62

Zoccola, R.; Di Blasio, A.; Bossotto, T.; Pontei, A.; Angelillo, M.; Dondo, A.; Goria, M.; Zoppi, S. Validation of a novel diagnostic approach combining the VersaTREK™ System for recovery and Real-Time PCR for the Identification of Mycobacterium chimaera in water samples. Microorganisms 2021, 9, 1031

Pavlik I, Ulmann V, Hubelova D, Weston RT. Nontuberculous Mycobacteria as Sapronoses: A Review. Microorganisms. 2022 Jul 3;10(7):1345

Ratnatunga CN, Lutzky VP, Kupz A, Doolan DL, Reid DW, Field M, Bell SC, Thomson RM, Miles JJ. The Rise of Non-Tuberculosis Mycobacterial Lung Disease. Front Immunol. 2020 Mar 3;11:303.

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