Low rate of emergence of drug resistance in sputum positive patients treated with short course chemotherapy.

Tuberculosis Research Centre

Journal of Tuberculosis and Lung Diseases; 2001; 5; 40-45.          

Setting : Tuberculosis Research Centre, Chennai.

Objective : To study the emergence of drug resistance during treatment and relapse among sputum positive pulmonary tuberculosis patients treated with short-course chemotherapy regimens.

Design : Retrospective analysis of randomized clinical trials using the following regimens: 2HRZE 7 /6HE 7 , 2HRZE 2 /4HRE 2 , 2HRZE 3 /4HR 2 and 3HRZE 3 /3HR 2 . Emergence of resistance was analysed in patients with unfavourable response/relapse based on culture and susceptibility reports.

Results : Of 1817 patients studied, 1435 (79%) had susceptible strains prior to treatment; 2% of these had an unfavourable response, 7% relapsed and 1% had emergence of resistance to isoniazid, rifampicin, or both. In 320 patients with initial isoniazid resistance, 19% had an unfavourable response and 13% relapsed, while resistance to rifampicin emerged in 11%. Treatment outcomes were similar whether patients received three or two drugs in the continuation phase. Data on resistance to ethambutol and pyrazinamide were not available.

Conclusion : In this study, the overall emergence of resistance to rifampicin occurred in only 2% of patients, despite the high level (18%) of initial resistance to isoniazid. Thus, standardized short-course treatment carries only a minimal risk of emergence of rifampicin resistance.

Key words : tuberculosis, emergence of drug resistance, short-course chemotherapy, rifampicin resistance

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