Molecular identification of mutations conferring resistance to rifampin, isoniazid and pyrazinamide among isolates from Iran.

Here, we aimed to determine the susceptibility of 70 isolates obtained from different regions of the country to 8 anti-tuberculosis (anti-TB) drugs and possible underlying mechanisms causing resistance to rifampin, isoniazid, and pyrazinamide. The susceptibility of 70 isolates of to anti-TB drugs was tested using proportion method. Strains showing resistance to the first line anti-TB drugs were subjected to PCR amplification and sequencing of the genes, promoter and intergenic regions to detect resistance conferring mutations. Overall, 77.1% and 77.1% of isolates were resistant to at least one of the tested first- and second-line drugs, respectively. Within the gene the highest rate of mutation was found in codons 531(450) (56.3%), and 533(452) (12.5%). Also, codons 315 (42.4%) of positions -48, -72 and -77 of (total= 3, 9.1%) and -15 of promoter region (33.3%) were the most altered positions in isoniazid resistant isolates. Only a single mutation was detected for among resistant isolates. High prevalence of resistance to essential anti-TB drugs among strains isolated from retreated tuberculosis cases is alarming issue necessitating immediate action to prevent the spread of drug resistant isolates in the country.