Rationale: Persons with cystic fibrosis (CF) are at high risk of nontuberculous mycobacterial (NTM) infection, with treatment requiring prolonged multidrug regimens that include macrolides. Although macrolides, specifically azithromycin, are used in the management of patients with CF with chronic Pseudomonas, macrolide-resistant NTM infections are of growing concern.
Objectives: To evaluate the relationship between chronic macrolide use and NTM infection among patients with CF included in the 2011 CF Patient Registry (CFPR).
Methods: We performed a nested case-control study: incident NTM cases were persons aged more than 5 years with at least one positive culture for NTM in 2011. Controls were persons with negative cultures in 2010 and 2011.
Measurements and main results: The 2011 CFPR included 27,112 patients; 5,403 (20%) were cultured for mycobacteria in 2010-2011 and met all inclusion criteria. Of these, 191 (4%) were NTM-positive in 2011 only (cases); 5,212 (96%) were NTM-negative in 2010 and 2011 (control subjects). Among the cases, 122 (64%) were culture-positive for Mycobacterium avium complex (MAC) and 69 (36%) for M. abscessus. Azithromycin use in 2010 was less frequently reported among MAC cases (57%; odds ratio = 0.7, P < 0.05) and M. abscessus cases (51%; odds ratio = 0.5, P < 0.01) than in control subjects (66%). Among adolescents and adults, patients with the greatest number of years on chronic macrolides were the least likely to develop incident NTM in 2011 (P < 0.01).
Conclusions: Patients with incident NTM infections from either MAC or M. abscessus were less likely to have had chronic azithromycin treatment in the past year. However, because macrolide monotherapy may lead to macrolide resistance, routine screening for NTM should be considered for persons with CF.