Molecular Analysis of Isoniazid, Rifampin and Streptomycin Resistance in Mycobacterium tuberculosis Isolates from Patients with Tuberculosis in Düzce, Turkey

The aim of this study was to use DNA sequencing analysis to analyze the mutations in the most commonly targeted genes (katG, inhA, rpoB, rpsL) in isoniazid (INH)-, rifampin (RIF)- and streptomycin (SM)-resistant Mycobacterium tuberculosis strains obtained from subjects in Düzce, Turkey. Four isolates were found to be INH-resistant, 3 were RIF- resistant and 5 were SM-resistant, out of a total of 52 M. tuberculosis strains. In 3 of the 4 INH-resistant strains, a mutation in the katG gene in codon 315 appeared as AGC→ ACC (Ser→ Thr), and the other INH-resistant strain showed a mutation in the katG gene in codon 314 as ACC→ CCC (Thr → Pro). There were no mutations in the inhA gene in INH-resistant isolates. Two of the 3 RIF-resistant strains were found to have mutations in the rpoB gene in codon 516 appearing as GAC→ GTC (Asp→ Val), and the other RIF-resistant strain has a mutation in the rpoB gene in codon 531 as TCG→ TTG (Ser→ Leu). These 3 RIF-resistant strains are also INH-resistant. All 5 SM-resistant strains have mutations in the rpsL gene in codon 43 appearing as AAG→ AGG (Lys→ Arg). Thus, we found common gene mutations that bring about the resistance of M. tuberculosis to antituberculosis drugs in all of our isolates from Düzce. To the best of our knowledge, the ACC→ CCC (Thr→ Pro) mutation in the katG gene in codon 314 has not been previously defined.