Nontuberculous mycobacteria isolated during the treatment of pulmonary tuberculosis

Background: The significance of nontuberculous mycobacteria (NTM) isolated from a patient during therapy for pulmonary tuberculosis (TB) is uncertain. We investigated the frequency and clinical significance of NTM isolated from patients receiving anti-TB treatment. Methods: We conducted a retrospective cohort study of all patients with culture-confirmed pulmonary TB, and identified patients with respiratory cultures positive for NTM during therapy for pulmonary TB. Results: From January 2003 to December 2005, 958 patients were diagnosed with culture-confirmed pulmonary TB. NTM were isolated from 113 specimens in 68 (7.1%) patients during anti-TB treatment. The most frequently isolated NTM species were Mycobacterium abscessus (n = 35, 31%), Mycobacterium fortuitum (n = 17, 15%), Mycobacterium avium complex In = 9, 8%), and Mycobacterium gordonae (n = 9, 8%). Forty-eight (71%) patients had only one positive culture, white 20 (29%) had two or more positive cultures for NTM. Only two (3%) patients who had two or more positive culture after anti-TB treatment showed the same NTM species, which were M. abscessus. Conclusion: The isolation of NTM in patients with pulmonary TB is not uncommon during anti-TB treatment. However, this is likely the result of colonization, a transient infection, or specimen contamination. The co-existence of pulmonary TB and NTM lung disease may be rare but should be considered in patients with relatively virulent NTM species such as M. abscessus. (C) 2009 Elsevier Ltd. All rights reserved.