High Frequency of Mutations in the rpoB Gene in Rifampin-Resistant Clinical Isolates of Mycobacterium tuberculosis from Singapore

Rifampin (RIF) is a first-line antituberculosis drug. Resistance to RIF, in the majority of cases, has been associated with mutations within an 81-bp RIF resistance-determining region (RRDR) of the rpoB gene, which encodes the β subunit of the RNA polymerase (8). RIF acts by binding to the β subunit of the RNA polymerase, thus interfering with transcription and RNA elongation.