Objective: To assess the molecular mechanism of rifampin (RMP) resistance in clinical strains of Mycobacterium tuberculosis.
Design: The molecular nature of a part of the rpoB gene in 77 M. tuberculosis clinical strains isolated in Korea was analyzed using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and PCR-sequence analysis.
Results: Among 67 RMP-resistant isolates, 50 showed SSCP profiles different from that of an RMP-sensitive control strain, M. tuberculosis H37Rv, indicating the possible existence of a sequence alteration in this region of the rpoB gene, while 17 resistant isolates displayed SSCP profiles indistinguishable from that of the sensitive control strain. Subsequently, 17 clinical isolates whose SSCP profiles were difficult to distinguish from the control strain were subjected to sequence analysis. The analysis revealed that all 17 isolates did indeed contain mutations in the 81 bp region of the rpoB gene, which is associated with RMP resistance.
Conclusion: The results from our study clearly indicate that the molecular mechanism of RMP resistance in M. tuberculosis isolates from Korea involves alterations in the rpoB gene. In addition, this study suggests that PCR-direct sequence analysis works more efficiently and accurately than PCR-SSCP analysis for rapid screening of RMP-resistant M. tuberculosis clinical isolates.