Nontuberculous mycobacteria among patients with cystic fibrosis in the United States: screening practices and environmental risk

Rationale: Persons with cystic fibrosis (CF) are at greater risk of nontuberculous mycobacterial (NTM) infections than the general population. However, among patients with CF, geographic variation in prevalence is poorly understood.

Objectives: To describe the prevalence and screening practices of NTM among U.S. patients with CF.

Methods: CF Patient Registry data from 2010-2011 were obtained to estimate the prevalence of NTM among patients with CF 12 years of age or older by state. Climatic data were also obtained and predictors of NTM infection analyzed using regression analysis. Geographic clustering and mycobacterial culture rates by state were also assessed.

Measurements and main results: Among patients with CF 12 years of age or older, 58% had mycobacterial cultures; 14% were positive for NTM. Most states (n = 31) had a prevalence of 10-20%; seven states predominantly in the West and Southeast had a prevalence of 20% or greater, including Alaska, which cultured patients more frequently than any other state. Nearly 60% of positive cultures were for Mycobacterium avium complex, although this ranged by state, from 29% in Louisiana to 100% for Nebraska/Delaware. Significant (P < 0.002) spatial clustering of NTM was detected, centering in Wisconsin, Arizona, Florida, and Maryland. Higher saturated vapor pressure increased risk for NTM (odds ratio = 1.06; 95% confidence interval = 1.02-1.10). The proportion of patients cultured for mycobacteria varied greatly by state of residence (median = 46%; range = 9-73%).

Conclusions: NTM prevalence varies significantly among patients with CF by geographic area, and is largely influenced by environmental factors. However, NTM culture practices vary greatly, with some high-prevalence states screening less than 25% annually. Routine screening for all patients with CF is needed for timely detection.