Study of ethA gene sequence in Ethionamide resistant clinical isolates of Mycobacterium tuberculosis

Ethionamide (ETH) is a structural analog of isoniazid and secondary line anti-tuberculosis drugs. Both of Ethionamide and isoniazid target INHA protein in mycobacterium tuberculosis. This protein involved in mycolic acid biosynthesis. The purpose of this study is evaluation of sequence of ethA gene in order to detect mutations related to resistance to isoniazide in clinical mycobacterium tuberculosis isolates. In this study were evaluated 27 resistance and sensitive isolates to ethionamide. Because of length of this fragment (1470bp) were performed three reactions for each sample with ethA-10, ethA-8, ethA-9, ethA-4, ethA-5 and ethA-1 specific primers in PCR reaction. From 27 used clinical isolates, 23 strains were resistant and 4 isolates were susceptible to ETH. Results of electrophoresis were proved proper selection of primers and PCR conditions. DNA sequencing results were determined mutations at some points of the gene in the resistant isolates to ETH, but none of susceptible strains harbored mutations. According to the results it was proved that any mutations in each point of ethA gene could cause resistance to Ethionamid. Rapid molecular detection of the resistance is possible only via complete sequencing of total length of this gene.