Characterization of gyrA and parC mutations in ciprofloxacin-resistant Pseudomonas aeruginosa isolates from Tehran hospitals in Iran

Abstract

Background and objectives: Pseudomonas aeruginosa, a major cause of several infectious diseases, has become a hazardous resistant pathogen. One of the factors contributing to quinolone resistance in P. aeruginosa is mutations occurring in gyrA and parC genes encoding the A subunits of type II and IV topoisomerases, respectively, in quinolone resistance determining regions (QRDR) of the bacterial chromosome.

Materials and methods: Thirty seven isolates from patients with burn wounds and 20 isolates from blood, urine and sputum specimen were collected. Minimum Inhibitory Concentrations (MICs) of ciprofloxacin were determined by agar diffusion assay. Subsequently, QRDRs regions of gyrA and parC were amplified from resistant isolates and were assessed for mutations involved in ciprofloxacin resistance after sequencing.

Results: Nine isolates with MIC≥8 μg/ml had a mutation in gyrA (Thr83→Ile). Amongst these, seven isolates also had a mutation in parC (Ser87→ Leu or Trp) indicating that the prevalent mutation in gyrA is Thr83Ile and Ser87Leu/Trp in parC. No single parC mutation was observed.

Conclusion: It seems that mutations in gyrA are concomitant with mutations in parC which might lead to high-level ciprofloxacin resistance in P. aeruginosa isolates from patients with burn wounds and urinary tract infections.

Keywords: Ciprofloxacin resistance; Fluoroquinolones; GyrA; ParC; Pseudomonas aeruginosa.

Fig. 1.

Ciprofloxacin sensitivity test using Kirby-Bauer test

Fig. 2.

PCR products amplified with gyrA specific primers and electrophoresed on agarose gel

Fig. 3.

Comparison of gyrA PCR products sequences with P. aeruginosa PAO1 using CLUSTAL 2.1 multiple sequence alignment.

Fig. 4.

Comparison of parC PCR products sequences with P. aeruginosa PAO1 using CLUSTAL 2.1 multiple sequence alignment.