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

Int J Tuberc Lung Dis. 2001 Jan;5(1):40-5.


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 randomised clinical trials using the following regimens: 2HRZE7/6HE7, 2HRZE2/4HRE2, 2HRZE3/4HR2 and 3HRZE3/3HR2. 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, standardised short-course treatment carries only a minimal risk of emergence of rifampicin resistance.

MeSH terms

  • Antitubercular Agents / administration & dosage*
  • Chi-Square Distribution
  • Drug Administration Schedule
  • Female
  • Humans
  • India / epidemiology
  • Male
  • Retrospective Studies
  • Rifampin / administration & dosage
  • Treatment Outcome
  • Tuberculosis, Multidrug-Resistant / epidemiology*
  • Tuberculosis, Pulmonary / drug therapy*
  • Tuberculosis, Pulmonary / epidemiology*


  • Antitubercular Agents
  • Rifampin