Drug resistance in Mycobacterium tuberculosis strains isolated from re-treatment cases of pulmonary tuberculosis in Ethiopia: susceptibility to first-line and alternative drugs

Abstract

Setting: Addis Ababa Tuberculosis Demonstration and Training Center, Ethiopia.

Objectives: To determine the pattern of drug resistance among re-treatment cases of pulmonary tuberculosis (TB), to determine the risk factors associated with multi-drug resistant (MDR) TB, and to propose re-treatment regimens based on the patterns of susceptibility to first-line and alternative drugs.

Design: One hundred and seven Mycobacterium tuberculosis strains isolated from an equal number of re-treatment cases of pulmonary TB were included in the study. Drug susceptibility was determined by the Bactec method.

Results: About 50% of the strains were resistant to one or more of the first-line drugs and 12% of the strains were multi-drug resistant, i.e., resistant to both isoniazid and rifampicin. Previous treatment with rifampicin was the most important predictor of MDR-TB. All MDR strains were susceptible to amikacin, ciprofloxacin, ethambutol, ethionamide and clofazimine.

Conclusion: The WHO re-treatment regimen would theoretically be effective for the treatment of all non-MDR-TB patients in this study. A proposed 12-month re-treatment regimen for MDR-TB patients would include a fluoroquinolone in combination with streptomycin, pyrazinamide, isoniazid, ethambutol and clofazimine. There is an urgent need for more research to define safe and inexpensive treatment regimens for MDR-TB patients in low-income countries.