Examining the genomic role of gyrA in mycobacterial strains

Tuberculosis is a common, and in many cases fatal, infectious disease. This disease is caused by various species of mycobacteria, usually Mycobacterium tuberculosis. This bacterium shows intrinsic and acquired resistance to all kinds of antibiotics. An important mechanism of resistance to fluoroquinolones in Mycobacterium tuberculosis is the mutation in gyrA, a type II topoisomerase subunit. The aim of this study is to investigate the genomic role of gyrA in mycobacterial strains.In this cross-sectional study, ۱۲۰ isolates of Mycobacterium tuberculosis isolated from different samples, including sputum and respiratory secretions, were identified using biochemical methods. Antibiotic sensitivity and resistance were determined by molecular PCR. To investigate gyrA gene mutations in ciprofloxacin-resistant isolates, PRRFP was performed. BLAST software was used to compare gyrA gene sequence in resistant isolates.The highest level of resistance to ciprofloxacin in isolates was MIC>۳۱۰ μg/ml. Two mutations in gyrA gene were identified in resistant isolates. Also, this study showed that there is no relationship between MIC level in ciprofloxacin resistant isolates and mutation in gyrA gene.These results show that the mutation in the gyrA gene is one of the most important mechanisms of resistance to ciprofloxacin in clinical isolates of Mycobacterium tuberculosis, and it seems that the mutation in gyrA, along with several genes involved in the development of resistance, has increased resistance in different isolates.

Keywords:

gyrA , polymorphisms , Mycobacterium tuberculosis