RESUMEN
In view of the worldwide re-emergency of tuberculosis (TB) and the rise of pulmonary TB (TBP) resistant to the two main first line drugs, namely isoniazid (H) and rifampin (R), so called multidrug resistant TBP (MDR-TBP), it was considered necessary to carry out a national, non randomized, multicenter, prospective pilot survey to determine the rates of resistant Mycobacterium tuberculosis (MTB) in patients with no previous antituberculous treatment (primary resistance). A total of 30 health institutions were chosen (disseminated among the 14 districts of the country) with the most TBP cases reported in 1997, and asked to provide in a consecutive non random way, sputum samples from new smear positive TB patients starting the first working week of January until the last one of December 1998; these samples were processed for culture at the Tuberculosis Section of the Health Ministry Central Laboratory. Those that resulted positive for MTB underwent a test for resistance to the first line drugs used in this country (isoniazid, rifampin, pyrazinamide, ethambutol and streptomycin). A total of 348 MTB positive samples were collected. The rate of primary resistance to at least one drug was 3.3 percent and to H it was 0.3 percent, being these rates among the lowest in Latin America. For this reason further studies comprising the whole universe of new and already treated smear positive TB patients are to be performed in order to determine more accurately the primary resistance and acquired rates.