Abstract: ObjectiveTo study the mechanism of drug resistance in M. tuberculosis. MethodsM. tuberculosis virulent strain (H₃₇Rv) that was cultured in the different levels of rifampicin and 36 isolated strains with the Results of drug resistance were analyzed by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and sequence analysis. ResultsThe 7th generation of strain H₃₇Rv had abnormal PCR-SSCP profile, was confirmed rpoB gene mutation at codon 513 by DNA sequencing. Of 36 clinical isolates, 63.9% strains (23/36) had rpoB mutations. The mutation sites of 5 clinical isolates were the same as that of induced strains H₃₇Rv. Conclusions Stimulating constantly tubercle bacillus with rifampicin is an important reason that cause rifampicin-resistant tuberculosis.

Key words: mycobacterium tuberculosis, rifampin, drug resistance,bacterial, polymerase chain reaction, polymorphism,single-stranded conformational