Trends of drug resistant Mycobacterium tuberculosis in a tertiary tuberculosis center in Iran

OBJECTIVE: To determine the drug resistance pattern to first line antituberculous drugs in National Research Institute of Tuberculosis and Lung Disease and to compare resistant rates with previous studies.

METHODS: An anterograde cross-sectional study was performed. The study includes all adults with documented pulmonary tuberculosis (TB) that were hospitalized in National Research Institute of Tuberculosis and Lung Disease in Tehran, from June 2003 to September 2004. Demographic characteristic, TB categories, and drug susceptibility test results were recorded. Two previous studies regarding drug susceptibility in Iran were selected as historical controls.

RESULTS: One hundred and ninety-six new cases and 68 previously treated patients were enrolled in the study. The strains of 61% of new patients and 21% of previously treated patients were fully sensitive to all drugs. The most common resistance was streptomycin (27%) followed by isoniazid (23%) in new cases. Multiple drug resistant strains were noted in 2.6% (95% CI 0.8% to 5.8%) of new cases versus 56% (95% CI 43% to 68%) in previously treated group. The frequency of primary drug resistance to isoniazid was 9.8%-15% or streptomycin 9.8%-13% in the previous studies (p<0.00001).

CONCLUSION: While these rates may not reflect the true prevalence of drug resistance on a national scale, it does partially demonstrate some defects in the existing tuberculosis control program. The significant increase of isoniazid and streptomycin resistance in the last few years would present a serious challenge to effective management of TB.