Drug resistance pattern and outcome of treatment in recurrent episodes of tuberculosis.

Patterns of drug resistance in recurrent cases of tuberculosis may be different than in those without a history of treatment. In this retrospective study, the drug resistance pattern and outcome of treatment with DOTS category I (CAT I) regimen was compared in 63 recurrent cases and 872 new cases of pulmonary tuberculosis from April 2003 to January 2008 at the National Research Institute of Tuberculosis and Lung Disease in Tehran, Islamic Republic of Iran. Resistance to isoniazid and ethambutol was significantly more common in recurrent cases, but there were no differences in rates of resistance to rifampin, pyrazinamide, streptomycin or the rate of multi-drug resistant strains. Resistance to streptomycin was the most common. No significant differences in treatment outcome and deaths were found between the 2 groups. Due to the low frequency of multi-drug resistance in the recurrent cases, a CAT I regimen may be suitable for empirical therapy before drug sensitivity results become available.