A Geospatial Epidemiologic Analysis of Nontuberculous Mycobacterial Infection: An Ecological Study in Colorado

Abstract

Rationale: Nontuberculous mycobacteria (NTM) are ubiquitous environmental microorganisms. Infection is thought to result primarily from exposure to soil and/or water sources. NTM disease prevalence varies greatly by geographic region, but the geospatial factors influencing this variation remain unclear.Objectives: To identify sociodemographic and environmental ecological risk factors associated with NTM infection and disease in Colorado. Methods:We conducted an ecological study, combining data from patients with a diagnosis of NTM disease from National Jewish Health's electronic medical record database and ZIP code-level sociodemographic and environmental exposure data obtained from the U.S. Geological Survey, the U.S. Department of Agriculture, and the U.S. Census Bureau. We used spatial scan methods to identify high-risk clusters of NTM disease in Colorado. Ecological risk factors for disease were assessed using Bayesian generalized linear models assuming Poisson-distributed discrete responses (case counts by ZIP code) with the log link function.Results: We identified two statistically significant high-risk clusters of disease. The primary cluster included ZIP codes in urban regions of Denver and Aurora, as well as regions south of Denver, on the east side of the Continental Divide. The secondary cluster was located on the west side of the Continental Divide in rural and mountainous regions. After adjustment for sociodemographic, drive time, and soil variables, we identified three watershed areas with relative risks of 12.2, 4.6, and 4.2 for slowly growing NTM infections compared with the mean disease risk for all watersheds in Colorado. This study population carries with it inherent limitations that may introduce bias. The lack of complete capture of NTM cases in Colorado may be related to factors such as disease severity, education and income levels, and insurance status.Conclusions: Our findings provide evidence that water derived from particular watersheds may be an important source of NTM exposure in Colorado. The watershed with the greatest risk of NTM disease contains the Dillon Reservoir. This reservoir is also the main water supply for major cities located in the two watersheds with the second and third highest disease risk in the state, suggesting an important possible source of infection.

Assessment of Soil Features on the Growth of Environmental Nontuberculous Mycobacterial Isolates from Hawai'i

“…Yet, soil components such as natural rock, sand, or clay may also impact NTM presence and diversity. A study by Lipner et al reported increasing clay concentrations as protective against NTM, while increasing silt concentrations was associated with NTM infection (11). In this same study and another, higher manganese concentration was associated with disease prevalence (9,11).…”

Epidemiology of Nontuberculous Mycobacteriosis

“…68 Another factor that appears to influence risk of PNTM is the watershed affiliated with a patient's area of residence. 69 Using data on non-CF NTM patients treated at National Jewish Health and residing in Colorado, researchers found that three specific watersheds were at increased risk of PNTM, all of which appear to share a similar water source and distribution mechanism. 69 Soil and dust have also been identified as potential sources of NTM exposure.…”

“…69 Using data on non-CF NTM patients treated at National Jewish Health and residing in Colorado, researchers found that three specific watersheds were at increased risk of PNTM, all of which appear to share a similar water source and distribution mechanism. 69 Soil and dust have also been identified as potential sources of NTM exposure. Aerosols generated from potting soils in households of PNTM patients were found to contain known pathogenic NTM species, including M. avium, M. intracellulare, and M. kansasii, some of which matched corresponding patient isolates by pulsed-field gel electrophoresis genotyping.…”

The Many Lives of Nontuberculous Mycobacteria

“…Aquatic environments can be significant NTM reservoirs, and water is increasingly recognized as an important NTM transmission medium. The aquatic environments in which NTM reside can be as small as a showerhead or as large as a watershed (46). The aquatic microenvironments in which NTM have been found are largely of human origin: NTM-containing water supplies have been responsible for outbreaks of NTM disease in hospitals (47,48), as well as for outbreaks among footbath customers (49,50), metal workers (51,52), and alternative-medicine users (53).…”

“…Environmental sampling revealed that mycobacteria comprised 1/3 of all microbes in the water of an indoor pool and 8/10 of all microbes in the surrounding bioaerosol (55). The aquatic macroenvironments in which NTM have been found include those of human origin (e.g., municipal water supplies) (56-59) but also natural watersheds (46) and lakes (60,61). Data from experimental models suggest that the water flow in aquatic micro-and macroenvironments is insufficient to prevent the formation of NTM biofilms (62), which facilitate NTM survival in numerous hostile environments (63).…”