Phenotypic and genotypic resistance of drug-resistant Mycobacterium tuberculosis isolates to first and second-line anti-TB drugs in Iran

Aims and objectives: Treatment of patients with drug-resistant tuberculosis is time-consuming and requires expensive drugs with more toxicity. Proper and timely identification of drug-resistant genotypes and determining the minimum inhibitory concentrations (MICs) alongside with the molecular basis of resistance can minimize the risk of further resistance development. Methods: Multidrug-resistant Mycobacterium tuberculosis (MDR-MTB) strains from different provinces were identified at Tehran Regional Reference Laboratory for Tuberculosis. Drug susceptibility testing for the first and second-line anti-TB drugs were performed and compared to the whole genome sequencing (WGS) results. Results: Simultaneous resistance to antibiotics included in each of the fluoroquinolones and second-line injectable drug families was observed in most of the MDR isolates. Sequencing was able to detect resistance to anti-TB drugs with a proper sensitivity. The most prevalent lineage among the Iranian MDR strains was Beijing. Conclusions: Mutations in drug resistance-related genes were mostly in accordance with the phenotypic drug susceptibility testing results. Drug-resistant tuberculosis can be identified quickly using molecular techniques. However, genetic background of resistance for some antibiotics were remained for more investigation.