Tuberculosis control and molecular epidemiology in a South African gold-mining community

Background Gold miners have very high rates of tuberculosis. The :contribut ion of infections imported into mining communities versus transmission with in them is not known and has implications for control strategies, Methods We did a prospective, population-based molecular and,conventional e pidemiological study of pulmonary tuberculosis in a group of goldminers. Cl usters were defined as groups of patients with Mycobacterium tuberculosis i solates with identical IS6110 DNA fingerprints. We compared the frequency o f possible risk factors in the clustered and nonclustered patients whose is olates had fingerprints with more than four bands, and re-interviewed membe rs of 45 clusters. Findings Of 448 patients, ten were excluded because they had false-positive cultures. Fingerprints were made in 419 of 438, of which 371 had more than four bands. 248 of 371 were categorised into 62 clusters. At least 50% of tuberculosis cases were due to transmission within the community. Patients who had failed treatment at entry to the study were more likely to be: in c lusters (adjusted odds ratio 3.41 [95% CI 1.25-9.27]). Patients with multid rug-resistant isolates were more likely to have failed treatment but were l ess likely to be clustered than those with a sensitive strain(0.27 [0.09-0. 83]). HIV infection was common (177 of 370 tested) but not associated with clustering. Interpretation Despite a control programme that cures 86% of new cases, mos t tuberculosis in this mining community is due to ongoing transmission. Per sistently infectious individuals who have:previously failed treatment may b e responsible for one third of tuberculosis cases. WHO targets for cure rat es are not sufficient to interrupt transmission of tuberculosis in this set ting. Indicators that are more closely linked to the rate of ongoing transm ission are needed.