Understanding the Epidemiology of Extensively Drug-Resistant Tuberculosis

摘要

A study of South African patients indicates that most cases arise through transmission rather than treatment failure. One of the major global healthcare concerns has been the emergence of extensively drugresistant tuberculosis (XDR-TB). Given the marked increase in cases seen in South Africa in the last 10 years, researchers undertook a detailed investigation to determine whether these cases were developing due to acquisition of drug resistance in patients with previously susceptible strains of TB, or to transmission of strains that were already extensively drug-resistant. Clinical and microbiologic data were collected on patients with XDR-TB in a single South African province from 2011 through 2014. Among 1027 patients identified with XDR-TB, a convenience sample of 404 patients was enrolled in the study; median age was 34 years, 50% lived in a rural setting, and 77% had HIV disease. Only 124 patients (31%) had been given prior treatment for multidrug-resistant tuberculosis, of whom 84% had treatment failure and 10% were lost to follow-up or transfer. Genotypic analysis, performed on isolates from 386 patients, showed that 323 patients (84%) were part of 31 case clusters; 30 of the clusters were from 2 to 14 patients in size, and one included 212 patients. Links between cases occurred in both households and healthcare centers. According to combined clinical and genotypic information, 61% of the patients had not received treatment and were in defined clusters; these patients represented the minimum number who could have acquired XDR-TB by transmission from another patient.