The relation of qnr genes to the induction of resistance to ciprofloxacin in Escherichia coli

Urinary tract infection (UTI) caused by Escherichia coli is a common infection. Fluoroquinolones are frequently used for treatment of UTI and improper use of these antibiotics has led to antibiotic resistance. Ciprofloxacin is a fluoroquinolone antibiotic used commonly for the treatment of UTI. From March to September 2014, we collected 1723 urine samples from four hospitals in Rasht. After culture & identification of E.coli, antibiogram was performed using ciprofloxacin disk. Plasmid DNA was extracted for amplification of qnrA, qnrB and qnrS.PCR products were electrophoresed on 2 % agarose gel containing syber safe. Using SPSS version 18, data analysis was performed by χ2 test. Of 309 isolated E.coli strains, 139 strains were resistant to ciprofloxacin among which, 96 (69.1%), 103 (74.1%) and 8 (5.8%) samples were carrying qnrS, qnrB and qnrA genes respectively. 9 strains were carrying qnrS, qnrB and qnrA genes simultaneously. Comparison of qnr genes in susceptible and resistant strains to ciprofloxacin showed that qnrS gene was associated with ciprofloxacin resistance. It is necessary to prevent the improper use of antibiotic because of increasing antibiotic resistance. Since qnr genes were detected in some susceptible strains, some other mechanisms such as mutation could be involved in the development of ciprofloxacin resistance.