High frequency of first-line anti-tuberculosis drug resistance among persons with chronic pulmonary tuberculosis at a teaching hospital chest clinic

Abstract

INTRODUCTION: The burden of MDR-TB is unknown in areas that do not have drug susceptibility testing (DST), but its frequency is expected to be higher in previously treated cases. Where DST is not available the WHO recommended standardized retreatment (Category II) regimen is given to previously treated TB patients OBJECTIVE: To evaluate the frequency and pattern of drug resistance of Mycobacterium tuberculosis isolated from patients with chronic smear positive pulmonary tuberculosis. METHOD: We conducted a retrospective review of mycobacterial cultures and drug susceptibility testing (DST) performed on sputum samples collected, between January 2005 and September 2006, from 40 patients with pulmonary TB who had failed at least one standard retreatment regimen. Clinical data was extracted from patients' case notes. RESULTS: M. tuberculosis was recovered from 28 (70%) of the 40 patients. Of the 28 culture positive cases, 10 (36%) had resistance to at least rifampicin and isoniazid (multi-drug resistant TB), 22 (79%) isolates had resistance to streptomycin and 13 (46%) to ethambutol. Of the patients with a positive culture, only one (3.6%) had a fully susceptible organism. Of the 10 patients with MDR TB, 7 had received two or more retreatment courses. CONCLUSION: The frequency of drug resistant TB was high among patients who failed at least one course of category II therapy. Effective combination regimens based on DST is necessary in patients who remain smear positive on the standardized retreatment regimen.