Mycobacterium tuberculosis
is the bacterium that causes tuberculosis (TB), a leading cause of death from infectious disease worldwide. Rapid diagnosis of resistant strains is important for the control of TB. Real-time polymerase chain reaction (RT-PCR) assays may detect all of the mutations that occur in the
M. tuberculosis 81-bp core region of the
rpoB gene, which is responsible for resistance to rifampin (RIF) and codon 315 of the
katG gene and the
inhA ribosomal binding site, which are responsible for isoniazid (INH). The goal of this study was to assess the performance of RT-PCR compared to traditional culture-based methods for determining the drug susceptibility of
M. tuberculosis. BACTEC
TM MGIT
TM 960 was used as the gold standard method for phenotypic drug susceptibility testing. Susceptibilities to INH and RIF were also determined by genotyping of
katG,
inhA and
rpoB genes. RT-PCR based on molecular beacons probes was used to detect specific point mutations associated with resistance. The sensitivities of RT-PCR in detecting INH resistance using
katG and
inhA targets individually were 55% and 25%, respectively and 73% when combined. The sensitivity of the RT-PCR assay in detecting RIF resistance was 99%. The median time to complete the RT-PCR assay was three-four hours. The specificities for tests were both 100%. Our results confirm that RT-PCR can detect INH and RIF resistance in less than four hours with high sensitivity.
