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

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.