Risk factors for pulmonary disease due to culture-positive M-tuberculosis or nontuberculous mycobacteria in South African gold miners

The aim of this study was to determine risk factors for disease due to nont uberculous mycobacteria (NTM) compared to those due to Mycobacterium tuberc ulosis in South African gold miners with pulmonary mycobacterial disease. A case/control study comparing tuberculosis and NTM cases amongst all patie nts with a positive sputum mycobacterial culture in 1995 was carried out. The 51 cases of disease due to NTM and 425 tuberculosis cases were similar with regard to age, education, home region, smoking habits and percentage o f CD4 cells. After adjustment for confounders, those with NTM were more lik ely to have had previous tuberculosis treatment (odds ratio (OR) 3.61; 95% confidence interval (CI) 1.9-6.9), have worked longer underground (p-value for trend=0.05) or have evidence of silicosis (OR 12.6; 95% CI 2.2-71) and were less Likely to drink regularly (OR 0.12; 95% CI 0.02-0.93) than patien ts with tuberculosis. In patients with disease due to NTM, 35.3% were human immunodeficiency virus-positive compared with 48.8% of tuberculosis patien ts (p=0.2) and an estimated 21% overall in the mines at the time of the stu dy. Previous tuberculosis treatment, silicosis and duration of underground work are even more strongly associated with disease due to nontuberculous mycob acteria than with tuberculosis. Attempts to reduce the incidence of all pul monary mycobacterial disease in this community should address recognized ri sk factors and ensure that those with tuberculosis are diagnosed, treated a nd cured.