Exposure Pathways of Nontuberculous Mycobacteria Through Soil, Streams, and Groundwater, Hawai'i, USA

摘要

Although uncommon, nontuberculous mycobacterial (NTM) pulmonary infection in the Hawaiian Islands has a relatively high incidence and mortality compared to the mainland U.S. As a result, this study examines the possible geological and hydrological pathways by which NTM patients may become infected, including the environmental conditions that may favor growth and transport. Previously suggested infection routes include the inhalation of NTM attached to micro‐droplets from infected home plumbing systems and aerosolized dust from garden soil. In this study, we evaluate the possible routes NTM may take from riparian environments, into groundwater, into public water supplies and then into homes. Because NTM are notoriously hydrophobic and prone to attach to surfaces, mineralogy, and surface chemistry of suspended sediment in streams, soils, and rock scrapings suggest that NTM may especially attach to Fe‐oxides/hydroxides, and be transported as particles from losing streams to the aquifer on time‐scales of minutes to days. Within the aquifer, flow models indicate that water may be drawn into production wells on time scales (months) that permit NTM to survive and enter domestic water supplies. These processes depend on the presence of interconnected fracture networks with sufficient aperture to preclude complete autofiltration. The common occurrence of NTM in and around streams, in addition to wells, implies that the natural and built environments are capable of introducing a source of NTM into domestic water supplies via groundwater withdrawals. This may produce a persistent source of NTM infection to individuals through the presence of NTM‐laden biofilms in home plumbing. Plain Language Summary Nontuberculous mycobacteria (NTM) cause opportunistic lung infections in Hawai'i, USA at about 4–5 times the rate on the USA mainland. NTM are known to exist as biofilms in home plumbing in Hawai'i as well soils and in and around streams. This paper examines a plausible, if not probable, pathway for NTM to be transported from riparian zones, into losing stream stretches, and into aquifers. NTM‐bearing water may then enter public water supplies where, being chlorine resistant, they outcompete competitor microbes to establish biofilms in home plumbing. Key Points Nontuberculous mycobacterial (NTM) are found in soils and biofilms of riparian environments in Hawai'i NTM are likely transported from losing streams to aquifers Pumped wells draw NTM into culinary water supplies and into homes. NTM are chlorine resistant and outcompete other taxa in home plumbing