Molecular Detection of gyrA, parC and oprD Mutation in Pseudomonas aeruginosa Isolates from a University Hospital of Isfahan, Iran during 2016

Excessive use of broad-spectrum antibiotics in hospitals has led to the emergence of highly resistant strains of Pseudomonas aeruginosa. The main mechanism of resistance of this bacterium to fluoroquinolones and carbapenems are the modification of type II topoisomerases (DNA gyrase and topoisomerase IV) and alterations in the OprD porin, respectively. The aim of this study was to examine for the occurrence of mutations related to fluoroquinolone resistance of gyrA and parC genes and mutational inactivation of oprD gene of clinical isolates using DNA sequencing technique.
A total of 60 P. aeruginosa isolates were collected from the hospitalized patients in the Intensive Care Units (ICUs) of Al-Zahra hospital located in Isfahan, Iran. The pattern of sensitivity to antibiotics was determined using CLSI disk diffusion and MIC methods. The assay was based on a DNA sequencing method using polymerase chain reaction (PCR) for amplification and sequencing of the selected genes.
The results show that replacement of Ile for Thr-83 in gyrA was the only replacement, while other substitutions not observed. No mutations were found in parC. The most frequent amino acid alterations were E185Q, P186G, and V189T, found in five resistance isolates, However, nucleotide insertions and deletions mutations not observed.
Our study suggested that mutation of gyrA and oprD genes may play a minor role in fluoroquinolone and carbapenem resistance and other mechanisms may contribute to the fluoroquinolone and carbapenem resistance of P. aeruginosa.