Molecular Study of Quinolone Resistance Determining Regions of gyrA Gene and parC Genes in Clinical Isolates of Acintobacter baumannii Resistant to Fluoroquinolone

Abstract

Introduction: Acinetobacterb aumannii (A. baumannii) is an important pathogen in health care associated infections. Quinolone resistance has emerged in this pathogen.Aims & Objectives:The aim of the present study was to determine the presence of mutations of gyrA gene and parC genes by Restriction Fragment Length Polymorphism Polymerase Chain Reaction (RFLP-PCR) among clinical isolates of A. baumanii.Materials and Methods:The study was carried out on 140 clinical isolates of A. baumannii. The isolates were subjected to molecular study of mutations of gyrA gene and parC genes by RFLP–PCR beside determination of Minimal Inhibitory Concentration (MIC) by macro dilution tube method.Results:The isolates of A. baumannii were resistant to ciprofloxacine and levofloxacin at MIC >4 µg/ml. The most isolates had MIC >128 µg/ml (42.3%). All resistant strains to ciprofloxacin of A. baumannii had mutations in gyrA and parC. The most frequent mutations were combined mutations in both genes (85.5%) and 5% had single mutation either in gyrA or parC. The most frequently combined mutations were associated with MIC >128 µg/ml (42.3%).Conclusion:From this study we can conclude that resistance to ciprofloxacin was common in clinical isolates of A. baumannii. The most frequent mutations were present in gyrA and parC. However, mutations in parC alone were not uncommon. Further large scale studies are required to elucidate the resistance pattern of A. baumannii and its molecular mechanisms.

Association between mutations in GYR A/B and PAR C/E genes of Acinetobacter Baumannii clinical isolates and Fluoroquinolones resistance

“…These results differed from Stone et al [24], who reported that disc diffusion technique turned into a great fast screening technique to MIC for detection of antimicrobial sensitivity. Our results were matching with Maysaa et al and Valentine et al [25,26].…”

“…The mixed mutations in those genes are related to remarkable decrease binding affinity for quinolones in the resistant organisms. Theses outcomes had been in settlement with Maysaa et al and Redgrave et al [25,27].…”

Acinetobacter baumannii Antibiotic Resistance Mechanisms

“…Quinolone resistance occurs via three different mechanisms: (i) target mutations in gyrase and topoisomerase IV, which weaken the respective quinolone–enzyme interactions; (ii) plasmid-borne resistance mediated by Qnr proteins, the AMEs AAC(6′)-Ib-cr and AAC(6′)-Ib-cr5, and by plasmid-encoded efflux pumps; and (iii) chromosome-derived resistance resulted by either low expression of porins or overexpression of chromosome-encoded efflux pumps [ 123 , 124 , 125 ]. A recent review reported resistance of A. baumannii to fluoroquinolones between 50% and 73% of cases, while the respective resistance in developing countries during the last years displayed a marked increase reaching 75% to 97.7% [ 98 , 126 ]. Table 4 lists all recorded quinolone-specific resistance mechanisms for A. baumannii.…”

“…Although a single point mutation in DNA gyrase is usually not enough for resistance to fluoroquinolones in A. baumannii (maybe only against levofloxacin; single parC mutations link with ciprofloxacin resistance), concurrent mutations within QRDR regions of the gyrA and parC genes are linked with significantly higher level of quinolone resistance [ 130 , 131 ]. Alterations in gyrB and parE genes are of minor significance [ 126 ].…”

Multidrug-resistant Acinetobacter baumannii outbreaks: a global problem in healthcare settings

“…These mutations are sequential, as primary mutations in gyrA81 are followed by mutations in parC88 and parC84 in A. baumannii. However, a study described strains carrying mutations in only the parC gene, revealing the involvement of other resistance mechanisms for fluoroquinolone 23 - 24 .…”