Association between mutations in gyrA and parC genes of Acinetobacter baumannii clinical isolates and ciprofloxacin resistance

We investigated the contribution of gyrA and parC mutational mechanism in decreased ciprofloxacin susceptibility of Acinetobacter baumannii isolated from burn wound infections. Ciprofloxacin susceptibility of 50 A. baumannii isolates was evaluated by disk diffusion and agar dilution methods. PCR and sequencing were performed for detection of mutation in gyrA and parC genes. The 44 and 4 isolates of A. baumannii exhibited full and intermediate-resistant to ciprofloxacin, respectively. Overall, the 42 isolates with double mutations of gyrA and parC genes showed a higher level of ciprofloxacin resistance than the 3 isolates with single mutations of gyrA or parC. Simultaneous mutations in gyrA and parC genes are expected to play a major role in high-level fluoroquinolone resistance in A. baumannii; albeit a single mutation in DNA topoisomerase IV could occasionally be associated with intermediate-resistance to these antimicrobials.