Drug-Resistant TB Among Gold Miners in South Africa

Poor adherence to treatment protocols contributes to TB drug resistance. Prompted by a TB outbreak at a gold mine in South Africa in 2003, investigators assessed the evolution of drug resistance at this mine, which has a well-functioning TB-control program. Mine employees and their dependents (population, about 25,000 per year) were eligible for the study.

Employees who had new lesions detected on biannual chest radiographic screening — and individuals with self-reported suspected TB and symptoms of the disease — were referred for TB investigation. All Mycobacterium tuberculosis isolates were tested for susceptibility to isoniazid and rifampin; testing for second-line drugs was also available. Patients with bacteriologically confirmed TB were treated according to WHO guidelines. They were hospitalized in a TB or multidrug-resistant (MDR)-TB ward, equipped with ultraviolet lights and open ventilation, until consecutive sputum smears were negative for 2 consecutive weeks (or, for those with MDR-TB, 3 successive months), and then released to supervised outpatient treatment. Adherence rates were reported to be 95% to 98%.

From January 2003 through November 2005, TB was diagnosed in 3003 individuals (48% with new pulmonary TB, 25% with pulmonary TB requiring retreatment, and 27% with extrapulmonary TB). Thirty percent of cases were identified by active screening. Overall, 108 isolates (4%) were MDR, including 31 that were highly resistant. Among the 128 patients with drug-resistant TB, only 31% completed treatment and had confirmed bacteriological cure; 35% died, including 37% of the 84 known to be HIV infected. Based on epidemiologic data and genotypic analysis of isolates, the investigators estimated that 71% of the drug-resistant cases resulted from transmission of resistant strains rather than from acquired drug resistance.