Detection of Rifampin-resistance in Mycobacterium tuberculosis

ABSTRACT

Control of tuberculosis is threatened by widespread emergence of drug resistance in Mycobacterium tuberculosis. Understanding the molecular basis of resistance might lead to development of novel rapid methods for diagnosing drug resistance. Rifampin is a key component among therapeutic regimens for the tuberculosis; therefore, patients who have drug resistance do not convalesce satisfactorily. The molecular mechanism of resistance to rifampin in M. tuberulosis has been elucidated. Substitutions of a limited number of highly conserved amino acids encoded by the rpoB gene are responsible for the ""single-step"" high-level resistance of M. tuberculosis to rifampin. Currently, two genotype-based protocols allow drug test from minimally grown cultured materials: (i)mutation identification by direct sequencing of PCR-amplified material. and (ii)mutation screening by PCR-SSCP. The purpose of this study is to evaluate the usefulness of the both methods. A sample of 75 isolates of M. tuberculosis was studied, and it inculded 36 rifampin-resistant strains and 39 rifampin-sensitive strains by conventional methods. Mutaions were identified in 36 rifampin-resistant isolates but in none of 39 sensitive isolates. All mutations were clustered within a region of 23 amino acids. Both methods allow detection of rifampin resistance in 2 to 3 days and will thus help in the early management of infection by M. tuberculosis.