Detection of gyrA gene mutations In quinolone – resistant clinical isolates of Pseudomonas aeruginosa

Abstract

P.aeruginosa is a ubiquitous environmental organism and is a major opportunistic pathogen causing human infections. Fluoroquinolones have been widely used for the treatment of P.aeruginosa infections; however, P.aeruginosa is capable of acquiring resistance during antibiotic therapy. Emergence of antibiotic resistance in P.aeruginosa results in severe adverse outcomes. In P.aeruginosa, the mechanisms of resistance to fluoroquinolones are known to be the modification of DNA gyrase and topoisomerase IV, decreased penneability of the cell wall, and multi-drug efflux systems. Alterations in DNA gyrase or topoisomerase IV caused by mutations in the. so-called quinolone -resistance-determining region (QRDR) appear to play a. major role in fluoroquinolone resistance in clinical isolates of P.aeruginosa. Inour study, we aimed at the detection of possible mutation(s) within the QRDR of the gyrA gene among quinolone-resistant clinical P. aeruginosa isolates. Three hundred swabs were collected by the managing physician from t the external, middle ears, and the sinuses of patients attending the out• / patient clinic of the Alexandria University Students Hospital and the Health I Insurance Hospital. One hundred and twenty six P.aeruginosa isolates were J recovered from these swabs, they were identified by observing the characteristic colonial morphology, pigment production, characteristic grape- like smell of aminoacetophenone, positive oxidase test, culture on cetrimide agar and incubation at 42C. The API 20E system was used for confident identification of non-pigmented isolates. In our study, P.aeruginosa was the most commonly encountered organism from cases of chronic suppurative otitis media (CSOM) represented by a percentage of 43.8 %. It was also the predominant pathogen in cases of chronic external otitis (66.7%). Antibiotic sensitivity was done by the Bauer Kirby technique. Amongst the 126 P.aeruginosa isolates, twenty eight (22.2%) ofloxacin • resistant isolates were detected (all of them were recovered from patients suffering from CSOM). The resistance profile of those ofloxacin - resistant •. isolates to other antibiotics was determined in an attempt to identify those antibiotics with the best spectrum of activity and to describe the therapeutic approach that can be used to face these ofloxacin - resistant isolates.