The frequency of point mutations associated with resistance to isoniazid and rifampin among clinical isolates of multidrug-resistant Mycobacterium tuberculosis in the west of Iran

Abstract Global increasing broad-spectrum resistance to many antibiotics established Tuberculosis (TB) infections as worldwide health issue. The rising prevalence of multidrug-resistant (MDR) Mycobacterium tuberculosis (MTB) isolates around the world is a therapeutic challenge. Monitoring of resistance to anti-TB drugs is essential to implement the strategies to control tuberculosis. This study was aimed to identify the point mutations associated with resistance to isoniazid (INH) and rifampin (RIF) antibiotics by Polymerase chain reaction (PCR) and reverse hybridization methods in clinical isolated samples of MDR Mycobacterium tuberculosis in the west of Iran. Phenotypic and biochemical methods were used for the identification of TB strains. Then proportion and GeneXpert methods were used to determine resistance isolates. The DNA was extracted, and finally, PCR and reverse hybridization methods were performed to identify the mutations. Among 54 isolates of MTB, 22 isolates were INH and RIF susceptible, and 32 isolates were diagnosed as MDR isolates. Of 32 MDR isolates, 22 cases (%70) had a mutation in katG codon of 315, 1 case inhA (%3) and 9 (%28) isolated had no detectable mutation. About rifampin, the mutations associated with rpoB gene in codons 531, 516 and 626 comprised (n = 21, %66), (n = 7, %22) and (n = 1, %3) respectively and in 3 (%9) isolates no mutations were found. The sensitivity, specificity and accuracy for INH (%71, %100, %83) and rifampin (%91, %100, %94) obtained, also PPV and NPV were determined for INH (%100, %70), RIF (%100, %88) respectively. Our results showed that MDR isolates with mutations in the katG 315 and rpoB 531 regions are epidemic strains in our study area. Also, our results suggest that TB Resistance line probe assay (AID) method has high sensitivity for detection of point mutations among isoniazid- and rifampin- resistant TB isolates. However, gold-standard phenotypic methods must always confirm the molecular drug susceptibility test results.