Investigation of plasmid-mediated resistance mechanisms in quinolone resistant clinical escherichia coli isolates

Quinolones are commonly used for treating infections caused by Gram-negative microorganisms such as Escherichia coli. However, quinolone resistance has spiked up due to this very common empirical utilization of these antibiotics. The aim of this study is to investigate the presence of plasmid mediated quinolone resistance genes qnr, aac(6')-Ib ve qepA in 103 Escherichia coli isolates which were revived in Bacteriology Laboratory of Medical Microbiology Division of Adnan Menderes University Medicine Faculty Teaching Hospital between January 2012 and December 2013. Izolates from various clinical specimens have been examined for ampicillin, ampicillin/sulbactam, cefazolin, ceftazidime, cefotaxime, cefoxitin, cefuroxime, gentamicin, tobramycin, amikacin, ciprofloxacin, levofloxacin, norfloxacin, ofloxacin, nalidixic acid, piperacillin-tazobactam, ertapenem, imipenem, meropenem, trimethoprim-sulphamethoxazole antibiotic susceptibilities via disc diffusion method. Ciprofloxacin, levofloxacin, ofloxacin ve norfloxacin MIC values of these isolates have been established via microdilution method. Then, qnrA, B, S, C, aac(6')-Ib and qepA resistance genes have investigated by PCR. Plasmid-mediated quinolone resistance genes have been found in 62 (%60,19) of quinolone resistant Escherichia coli isolates. Most common found plasmid-mediated resistance gene was aac(6')-Ib (%52,42). qnrS (%3,88), qepA (%1,94) and qnr B (%0,97) have been established respectively. qnrS and aac(6')-Ib have been found in one isolate at the same time (%1). Neither qnrC nor qnrA resistance genes have not been found in our isolates. In correlation with the literature, the most common plasmid-mediated resistance gene was aac(6')-Ib in our study. Since a significant ESBL positivity and tobramycin and ampicillin resistance have been revealed in aac(6')-Ib positive isolates, it has been substantiated that other resistance patterns frequently accompany this resistance gene.