Background & Objective: Tuberculosis is a diseases which is severely threatening the individuals health and is spreading quickly. Moreover, the appearance of new strains resistant to drugs has complicated the issue. Since there is no information available regarding the present drug-resistance situation of patients suffering from tuberculosis in Mashhad, this study was conducted to determine the prevalence of this resistance in this city.

 Methods: To determine prevalence of anti-tuberculosis drug resistance in Mashhad, drug sensitivity of 75 M. tuberculosis strains isolated from patients with pulmonary and extra-pulmonary tuberculosis from 20 Feb. 2002 to 20 Aug. 2002 was studied using the indirect proportion method. Every strain was tested against Rifampicin (RMP), Isoniazid (INH), Ethambutol (ETM), and Streptomycin (STM). Medical records of the patients were reviewed. Patients with no or less than 1 month treatment were defined as new cases and those previously treated for more than 1 month were defined as previously treated cases.

 Results: Of 75 isolates, 70(93.33%) were from new and 5(6.66%) from previously treated cases. 68 patients (90.66%) were suffering from pulmonary and 7(9.33%) from extra-pulmonary tuberculosis. Of 75 isolates, 23(36%) were resistant to at least one anti-tuberculosis drug. The highest rate of resistance was observed to streptomycin. Three of the 75 strains (4%) were resistant to all four drugs. 1.43% and 40% of strains isolated from newly and previously treated patients respectively were multidrug resistant.

 Conclusions: In this study new cases with MDR-TB were less prevalent compared to other studies. Most drug resistance and MDR-TB were associated with previous treatment. Continual evaluation of drug resistance following DOTS implementation seems to be necessary.