Nontuberculous mycobacteria - Defining disease in a prospective cohort of South African miners

A gold mining work force was followed prospectively over 1 yr for sputum no ntuberculous mycobacterial (NTM) isolates. NTM were isolated from 118 men, of whom 32 (27%) met the American Thoracic Society (ATS) case-definitions f or pulmonary NTM disease (23 M. kansasii, seven M. scrofulaceum, one M. avi um, and one M. abscessus). Determining isolate significance was difficult b ecause most men had been started on presumptive TB treatment before isolate identification (70%). Histologic criteria were considered inappropriate fo r this high M. tuberculosis incidence population, particularly for patients who had stabilized on presumptive TB treatment. Among men not meeting case -definitions, indicators of disease were significantly more prevalent for M . kansasii than for M. fortuitum, the local laboratory contaminant (ORs: 6. 5 for cough, 7.2 for smear-positivity, 36.0 for radiologic changes, and 14. 3 for presumptive TB treatment), suggesting underdiagnosis of M. kansasii d isease. Of 53 men with definite or possible M. kansasii disease, 18 (34%) w ere HIV-positive. HIV-associated M. kansasii disease occurred at an early s tage of immunosuppression (median CD4 count, 381 x 10(6)/L) with a good out come (83% cured after 12 mo of treatment). ATS case-definitions for NTM dis ease are difficult to apply in this population, and treatment decisions sho uld be guided by the pathogenic potential of the isolate.