Clinical and radiological features of pulmonary disease due to culture-positive M. tuberculosis or nontuberculous mycobacteria in South African gold miners.

Distinguishing whether pulmonary mycobacterial disease is due to Mycobacterium tuberculosis or nontuberculous mycobacteria (NTM) has important clinical and public health implications. There are limited data comparing these groups of patients, particularly from developing countries in the era of HIV infection. South African mineworkers have high rates of tuberculosis (TB), NTM disease and HIV infection. The study took place in a hospital serving four gold mines. All men with a positive sputum mycobacterial culture in 1995 were enrolled. Patients were interviewed, sputum and blood samples obtained and a chest radiograph taken. We compared clinical, laboratory and radiological features in those with TB with those with NTM disease (mainly Mycobacterium kansasii). Treatment outcomes are reported for those with pulmonary disease due to M. kansasii. The 425 patients with TB and 51 with NTM disease showed no significant difference in HIV status. Of patients with a positive smear, 91.3% (314/344) cultured M. tuberculosis. Patients with TB weighed less (p=0.03) and had lower haemoglobin levels (p<0.001). Those with NTM were less likely to have extensive radiographic changes (OR 0.27) than those with TB. Those with NTM were more likely to have silicosis (OR 9.7). Fourteen of the 36 patients with M. kansasii pulmonary disease had a positive culture at six months and a further 11 had a positive culture in the follow-up period. Patients with TB had features of more aggressive disease. The current practice of treating smear-positive patients as TB seems reasonable. Treatment failure and relapse were common in those with disease due to M. Kansasii.