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Drug-Resistant TB Among Gold Miners in South Africa

Among gold miners in South Africa (many of them HIV infected), TB drug resistance spread despite treatment adherence.

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.

Comment: The study population was extremely vulnerable to TB because of occupational risks, such as silicosis and congregate living, and high rates of HIV infection. The authors identified several potential interventions to reduce the spread of drug-resistant TB under such circumstances: more-rapid drug-susceptibility testing, integration of HIV and TB treatment programs, more-rigorous infection-control measures in hospitals, more-aggressive case finding, and pharmacokinetic studies to optimize treatment regimens and drug dosages for MDR-TB.

— Mary E. Wilson, MD

Published in Journal Watch Infectious Diseases February 3, 2010

Citation(s):

Calver AD et al. Emergence of increased resistance and extensively drug-resistant tuberculosis despite treatment adherence, South Africa. Emerg Infect Dis 2010 Feb; 16:264.

• Medline abstract (Free)

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