Nontuberculous Mycobacterial Infection in Patients With Cystic Fibrosis: A Multicenter Prevalence Study

OBJECTIVE: To determine file prevalence of nontuberculous mycobacterial infection in patients with cystic fibrosis. PATIENTS AND METHODS: We performed a prospective study in which patients with cystic fibrosis were followed for 2 years; the patients were recruited from specialized units and were all over 6 years old. Sputum samples collected every 6 months were stained with auramine-rhodamine and cultures were prepared with a liquid and a solid medium. When stains; or cultures were positive for res nontuberculous mycobacteria, 1 or 2 additional sputum samples were obtained from the patients, who were monitored closely to assess the need for specific treatment. We assessed the following clinical variables: age, sex, presence of pancreatic insufficiency, use of aerosol antibiotic therapy, and long-term azithromycin and inhaled or oral corticosteroid therapies. RESULTS: A total of 220 patients (119 women) with a mean age of 22.62 years (range, 6-74 years) were enrolled; of these 23.6% were receiving azithromycin. We prepared 1303 sputum samples for mycobacterial growth (range per patient, 4-68 samples); 65 samples from a total of 17 patients (7.72%) were positive: 17 by auramine-rhodamine staining and 48 by culture. Eighty-eight culture samples were contaminated and Mycobacterium tuberculosis was not isolated in any of the cases. The mycobacteria isolated were M avium complex (n=10), M abscessus (n=6), and M fortuitum (n=1). Two or more positive cultures were obtained in 9 patients, 5 of whom experienced clinical deterioration and were prescribed specitic treatment. No significant differences in clinical variables were found between patients with nontuberculous mycobacteria and those without. CONCLUSIONS: The prevalence of nontuberculous mycobacterial infection in patients with cystic fibrosis was not very high (7.72%), perhaps because azithromycin interfered with the growth of these bacteria. Patients with repeat isolations of mycobacteria should be monitored closely.