Clinical significance of isolation of nontuberculous mycobacteria in pulmonary tuberculosis patients

Abstract

Clinical significance of isolation of nontuberculous mycobacteria (NTM) from respiratory specimens in patients with pulmonary tuberculosis is unknown. This study aimed to investigate the prevalence and clinical impact of NTM in pulmonary tuberculosis patients. We retrospectively reviewed data of patients with culture-confirmed pulmonary tuberculosis from 2000 to 2006. Those in whom NTM were isolated from respiratory specimens collected within two months before and nine months after the index culture of tuberculosis was plated were compared with those without NTM. Patients were followed for one year after initiation of anti-tuberculous treatment. Among 2133 patients with pulmonary tuberculosis, 48 (2.3%) with multiple and 106 (5.0%) with one isolate(s) of NTM were identified. Another 144 without NTM were selected and compared. The one-year mortality rates were similar among three groups. Patients with multiple NTM isolates were more likely to be symptomatic, sought medical help earlier, had smear-positive respiratory specimens, and received anti-tuberculous treatment later than those with single/no isolate(s). Cavities were more commonly visualized radiographically in patients with multiple/single NTM isolate(s) than those without NTM isolates. The mean duration of anti-tuberculous treatment was 8.8 months for patients with multiple NTM isolates, significantly longer than that in patients with single (7.6 months) and no NTM isolate(s) (7.5 months). NTM were present in the respiratory tract of 7.3% of patients with pulmonary tuberculosis. Although the outcomes were similar, the presence of NTM was associated with different clinical manifestations and had a significant impact on the treatment of tuberculosis.