Mycobacterium kansasii and M-scrofulaceum isolates from HIV-negative SouthAfrican gold miners: incidence, clinical significance and radiology

SETTING: A South African gold mining hospital. OBJECTIVE: To investigate the clinical significance of non-tuberculous myco bacteria (NTM) isolates, and estimate NTM disease incidence in human immuno deficiency virus (HIV) negative miners. DESIGN: Retrospective case series describing clinical and radiological feat ures associated with NTM sputum isolates from HIV-negative miners between J anuary 1993 and July 1996, and a comparison group with Mycobacterium tuberc ulosis infection. RESULTS: Of miners with NTM isolates, 90% had been HIV-tested and 81% were HIV-negative. M. kansasii and M. scrofulaceum accounted for 202 (68%) and 4 1 (14%) isolates respectively. More than 80% of miners with M. kansasii or M. scrofulaceum were smear positive, and new cavitation was present in 78% and 74% respectively. Treatment failure occurred in 3% of M. kansasii and 1 2% of M. scrofulaceum patients. A normal pre-morbid radiograph was signific antly less common in NTM than M. tuberculosis patients (odds ratio 0.26 and 0.10 for M. kansasii and M. scrofulaceum, respectively). NTM disease incid ence, defined as NTM isolate plus new cavitation, was estimated at 66 and 1 2 per 100 000 person-years for M. kansasii and M. scrofulaceum, respectivel y. CONCLUSIONS: M. kansasii and M. scrofulaceum disease are common in HIV-nega tive South African gold miners. Most isolates are associated with new cavit ation against a background of silicosis or old TB scarring.