Contribution of gyrA and qnrA genes in Ciprofloxacin Resistant Ecsherichia coli Isolates from Patients with Urinary Tract Infections of Imam Khomeini Hospital of Tehran

Resistance to ciprofloxacin as the most common antibiotic for the treatment of urinary tract infections (UTIs) is increasing. In this study, the role of gyrA and qnrA genes among ciprofloxacin resistant Escherichia coli (E. coli) isolates from UTIs was evaluated.

During September to March 2014, urine samples were collected from patients with UTIs of Imam Khomaini hospital of Tehran. Bacterial identification was done based on standard tests. The antibiotic sensitivity test was performed based on the clinical and laboratory standards institute (CLSI) 2014 protocol and minimal inhibitory concentration (MIC) of ciprofloxacin was determined by E-test strips. DNA was extracted by the boiling method and assessment of gyrA (DNA gyrase (type II topoisomerase)) and qnrA genes was done by the polymerase chain reaction (PCR). Further sequencing was done for PCR confirmation and blasting.

All isolates were susceptible to carbapenems (100%) and 98.7% were susceptible to nitrofrontain. The highest resistance was towards piperacillin 85%, ampicillin 83.8%, sulfamethoxazole trimethoprim (SXT) 78.7%, ciprofloxacin 77.5%, and 75% tetracycline. Around 80% of the E. coli isolates were identified as multi drug resistant (MDR). All isolates with MIC of ≥ 4 μg/mL for ciprofloxacin were the candidates for DNA extraction, PCR, and sequencing. The gyrA and qnrA genes were detected in 100% and 39% of isolates, respectively. Mutations were found in the sequence analysis, yet the mean full change was related to change of serine to leucine at position 83 (S 83 L).

Finally, contribution of both mutated chromosomal gyrA genes and plasmidic qnrA resistance genes in some of the high ciprofloxacin resistant bacterial strains was found in this study, besides the overuse of antibiotics, which can increase the emergence of resistant strains