The expression of gyrI in ciprofloxacin resistant mutant of E. coli following treatment with ciprofloxacin

The spread of resistance to gram-negative bacteria, especially strains of Escherichia coli, has reduced the effectiveness of antibiotics, including ciprofloxacin in the treatment of infectious diseases. The main target of this antibiotic in Escherichia coli is DNA gyrase. GyrI is one of the inhibitors of DNA gyrase that binds to DNA gyrase to prevent the binding of ciprofloxacin. Therefore, the aim of this study was to investigate the expression of gyrI in a ciprofloxacin resistant mutant of Escherichia coli following treatment with ciprofloxacin. To evaluate gyrI expression, cell RNA was extracted at the exponential phase of growth and after cDNA synthesis, gyrI gene expression of ciprofloxacin resistant mutant was measured as compared to wild type strain by Real Time PCR. The results of Real Time PCR showed that the expression of gyrI gene was increased in ciprofloxacin resistant mutant in exponential phase of growth. Increased expression of gyrI in presence and absence of ciprofloxacin in comparison to the wild type strain was significant (P<0.05). Increased expression of this gene in presence and absence of ciprofloxacin in the mutant cell was 63 and 8 times of that in wild type strain, respectively. In conclusion, it seems that in ciprofloxacin resistant mutant GyrI overexpression in exponential phase of growth especially in the presence of ciprofloxacin is an important factor in DNA gyrase inhibition and resistance to ciprofloxacin.