Reduced risk of nontuberculous mycobacteria in cystic fibrosis adults receiving long-term azithromycin

Background Azithromycin reduces exacerbations in cystic fibrosis (CF) patients. Our aim was to investigate its association with nontuberculous mycobacteria isolation and macrolide susceptibility. Methods From 2006 to 2010, all adult CF subjects at Cochin Hospital (Paris, France) harboring at least one positive NTM isolate were identified (Cases). In a nested case–control study, each Case was individually matched for age and gender with up to 4 CF adults with no NTM isolate (Controls). Clinical data at the time of first NTM isolate (index date) in Cases were compared with those of Controls using multivariate conditional regression analysis. Results CF subjects with positive NTM isolates (Cases, n=41) were matched to 155 Controls. Among Cases, 48.7% had isolates from Mycobacterium avium complex and 58.5% from Mycobacterium abscessus complex, and 31 Cases fulfilled the 2007 American Thoracic Society criteria for NTM infection (ATS+ Cases). Cases and ATS+ Cases were more likely to have low body mass index and colonization with Aspergillus fumigatus. Azithromycin was associated with a two-fold reduction in NTM isolates. Only one M. avium complex isolate had acquired macrolide resistance. Conclusion These data suggest that azithromycin is a primary prophylaxis for NTM infection in CF adults.