Antituberculosis drug resistance among retreatment tuberculosis patients in a referral center in Taipei

Background ad Purpose: To determine the prevalence of antituberculosis drug resistance among retreatment tuberculosis patients in a referral center in Taipei. Methods: We reviewed the register of susceptibility testing of the mycobacteriology laboratory of the Chronic Disease Control Bureau to identify patients with positive culture for Mycobacterium tuberculosis in the year 2000-2001. Medical charts were reviewed to determine patients' tuberculosis treatment histories. Patients who had multidrug-resistant (MDR) tuberculosis, defined as documentation of isolates resistant to at least isoniazid and rifampin, were identified. Retreatment tuberculosis patients without prior evidence of MDR tuberculosis were classified into 3 categories, i.e., relapse, treatment after default and treatment after failure, and the frequency and patterns of antituberculosis drug resistance were determined. Results: A total of 317 patients who had received antituberculosis treatment for more than 1 month were identified. Among them, 183 were retreatment cases without prior evidence of MDR tuberculosis, including 93 with relapse, 57 with treatment after default, and 33 with treatment after failure. Among the 183 patients, the prevalence of resistance to any drug was 42.6%; 14.2% were resistant to 1 drug, 13.7% to 2 drugs, 7.1% to 3 drugs, 7.7% to 4 drugs or more, and 24.6% had MDR tuberculosis. The prevalence of any drug resistance among patients with relapse, treatment after default and treatment after failure was 33.3%, 42.1 %, and 69.7%, respectively, while the prevalence of MDR tuberculosis in these groups was 12.9%, 19.3% and 66.7%, respectively. Conclusions: If susceptibility results are unavailable, the World Health Organization-recommended retreatment regimen may be used in retreatment tuberculosis patients. However, the high proportion of MDR tuberculosis among patients with treatment after failure poses a challenge to the efficacy of the retreatment regimen.