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

Abstract

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 timescales 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.

Vanadium in groundwater aquifers increases the risk of MAC pulmonary infection in O’ahu, Hawai’i

“…In regions where vanadium concentrations are high, NTM abundance (or more pathogenic species) is likely increased in the water supply, thereby increasing the overall risk of exposure and infection. In a previous study in HI, Nelson et al 43 examined possible routes that NTM may take from the environment into groundwater, subsequently into the public water supplies, and ultimately into homes. The authors demonstrated through aquifer flow models that NTM may survive within the water supply over the course of months via interconnected fractured basalt networks before entering domestic water supplies.…”

Complete genome assembly of Hawai’i environmental nontuberculous mycobacteria reveals unexpected co-isolation with methylobacteria

“…Hawai’i has more NTM lung disease cases per capita than any other US state [ 5 ]. Our prior research of 62 households found that clinically important NTM species are prevalent in the Hawai’i environment [ 6 ] and may be the source of the high rate of NTM infections [ 7 , 8 ]. To more broadly study NTM diversity, a Hawai’i-based community science network involving more than 200 local students and teachers from 11 different schools collected more than 2,800 environmental samples from across O’ahu, Kaua’i, Hawai’i Island, and Maui [ 9 ].…”

Hawaiian Volcanic Ash, an Airborne Fomite for Nontuberculous Mycobacteria

“…abscessus , from Hawai'i household water biofilms and garden soil with a predominance of Mycobacterium intracellulare subsp. chimaera (referred to as M. chimaera henceforth), whose common recovery mirrored Hawai'i respiratory specimens (Honda et al., 2016 ; Nelson et al., 2021 ; Virdi et al., 2021 ). We also demonstrated that the indoor environments of Hawai'i are more likely to harbor respiratory relevant NTM compared to outdoor environments, particularly for M. chimaera (Virdi et al., 2021 ).…”

“…Wetlands, specific soil components, and geospatial variables have all been correlated with NTM presence in outdoor niches of Hawai'i (Glickman et al., 2020 ; Nelson et al., 2021 ; Virdi et al., 2021 ). However, a unique environmental feature of Hawai'i is active volcanism, including the Kīlauea Volcano on Hawai'i Island.…”