Non-Tuberculous Mycobacteria Exposure in Homes Via Shower Aerosols

Mycobacterium avium-intracellulare
Shower aerosols may be a significant source of non-tuberculous mycobacteria exposure in homes.

Shower aerosols may be a significant source of non-tuberculous mycobacteria (NTM) exposure in homes, according to study results published in the Annals of the American Thoracic Society.

NTM, including Mycobacterium avium complex (MAC), can opportunistically cause debilitating pulmonary disease in humans and potential sources of exposure in homes include point-of-use water sources such as taps and showerheads, as well as gardening soils. However, the health effects of NTM in home environments are poorly understood.

Therefore, researchers tested associations between MAC pulmonary disease (MAC-PD) and NTM colonization of 5 potential point-of-use sources of pathogen exposure in homes in Washington and Oregon. Samples were collected from bathroom faucets, kitchen faucets, shower aerosols, indoor soil, and outdoor soil based  on the hypothesis that aerosol generation during routine hygiene, cooking, and gardening is an important step in disease acquisition. They found that NTM was isolated more often in case homes (n=56) compared with control homes (n=51). In addition, NTM isolation from shower aerosols had a high odds ratio (odds ratio, 3.2; 95% CI, 1.1-8.9) associated with disease while other home environmental samples (tap water and soils) did not exhibit this association.

Among other study limitations, the researchers’ microbiologic and molecular methods may not have detected all NTM present in the samples, and some plates were lost to mold overgrowth and other problems.

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“Future epidemiological investigations should look more at residential exposures, including but not limited to shower aerosols, in the homes of individuals with compromised immune or pulmonary systems,” the researchers concluded.


Tzou CL, Dirac MA, Becker AL, et al. Association between Mycobacterium avium complex pulmonary disease and Mycobacteria in home water and soil: a case-control study [published online on October 23, 2019]. Ann Am Thorac Soc. doi:10.1513/AnnalsATS.201812-915OC