Abstract
Nontuberculous mycobacteria (NTM) that cause human disease can be isolated from household tap water. Easy-to-use physical methods to reduce NTM from this potential source of exposure are needed. Filters and UV disinfection have been evaluated for their ability to reduce numbers of waterborne non-NTM organisms from drinking water, but their efficacy in reducing NTM counts are not well-established. Thus, five commercially available disinfection methods were evaluated for their potential as practical, efficient, and low-cost methods to reduce NTM from tap water. First, suspensions of tap water–adapted Mycobacterium smegmatis were passed through either a point-of-use, disposable, 7-day or 14-day Pall-Aquasafe filter. The 7-day filter prevented passage of M. smegmatis in effluent water for 13 days, and the 14-day filter prevented the passage of M. smegmatis for 25 days. Second, a granular activated carbon filter system failed to significantly reduce Mycobacterium abscessus and Mycobacterium avium numbers. Third, suspensions of tap water–adapted M. abscessus, M. avium, and M. chimaera (“MycoCocktail”) were passed through the “LifeStraw GO” hollow-fiber, two-stage membrane filtration system. LifeStraw GO prevented passage of the MycoCocktail suspension for the entire 68-day evaluation period. Finally, two different water bottle UV sterilization systems, “Mountop” and “SteriPEN,” were evaluated for their capacity to reduce NTM numbers from tap water. Specifically, MycoCocktail suspensions were dispensed into Mountop and SteriPEN water bottles and UV treated as per the manufacturer instructions once daily for 7 days, followed by a once weekly treatment for up to 56 days. After 4 days of daily UV treatment, both systems achieved a >4 log reduction in MycoCocktail CFU. After the 56-day evaluation period, suspension and biofilm-associated CFU were measured, and a >4 log reduction in CFU was maintained in both systems. Taken together, physical disinfection methods significantly reduced NTM numbers from tap water and may be easy-to-use, accessible applications to reduce environmental NTM exposures from drinking water.
Highlights
There are an estimated 180,000 individuals living in the United States with nontuberculous mycobacterial (NTM) pulmonary disease [1]
M. smegmatis was recovered from the swabbed surface samples of the input side of the 7- and 14-day filters (77 and 57 colony forming units (CFU)/cm2, respectively), all effluent water passing through either the 7- or 14-day Pall filters over the 13- or 25-day test period were completely devoid of M. smegmatis
Because there is potential for Nontuberculous mycobacteria (NTM) in tap water to be ingested and refluxed to cause lung infections [29, 30], suggestions to reduce bacterial numbers in drinking water are important and timely
Summary
There are an estimated 180,000 individuals living in the United States with nontuberculous mycobacterial (NTM) pulmonary disease [1]. A proportion of individuals are at heightened risk for NTM infection and development of pulmonary disease. These include individuals with prior occupational lung damage (e.g., black lung, smoking, and COPD), bronchiectasis, prior infection with Mycobacterium tuberculosis, immunodeficiency due to HIV infection, and immunodeficiency due to cancer or chemotherapies [2, 3]. NTM are intimately associated with natural and built freshwater systems [8, 9] and linked to exposure from household showerhead water and biofilms by DNA fingerprint comparisons [10]. As relapse due to NTM reinfection or reactivation of latent infection occurs at frequencies between 25 and 50%, it is of value to identify methods to reduce environmental exposure to NTM in the built household environment
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