Molecular detection of mutations in gyrA, gyrB, parC, and parE genes in the quinolone resistance determining region among Pseudomonas aeruginosa isolated from burn wound infection

Background and Aim: The prevalence of fluoroquinolone resistance among Pseudomonas aeruginosa isolates, particularly in burn wound infections, has been increasing. The primary cause of ciprofloxacin resistance is attributed to genetic alterations in the quinolone resistance determinant region (QRDR). In this study, we evaluated the antimicrobial resistance profile and QRDR gene mutations in both ciprofloxacin-resistant and non-resistant strains of P. aeruginosa derived from burn wound patients. Materials and Methods: A total of ۳۰۰ samples were collected from patients with burn wound infections in Guilan, Iran. The isolates were identified as P. aeruginosa, and drug susceptibility tests were conducted using the agar disk diffusion method. DNA extraction and polymerase chain reaction (PCR) analysis were performed for the amplification and sequencing of gyrA, gyrB, parC, and parE genes in the QRDR region. Results: Resistance to Tobramycin, Gentamicin, Piperacillin, Ciprofloxacin, Ceftazidime, and Amikacin was observed in ۵۹.۳۲%, ۵۵.۰۸%, ۵۱.۶۹%, ۵۰.۸۴%, ۳۰.۵۰%, and ۲۶.۲۷% of the isolates, respectively. Forty-two (۳۵.۵۹%) isolates were multi-drug-resistant (MDR). The sequencing results in the QRDR region showed that the majority of mutations were in the gyrA gene, with ۸۵.۷۱% of these mutations being the substitution of threonine with isoleucine (Thr-۸۳ Ile) in ciprofloxacin-resistant strains. An unusual amino acid substitution at codon ۴۷۰ of the parE gene encoding DNA topoisomerase IV (Aspartic acid replaced by Asparagine) was observed in a ciprofloxacin-resistant strain. No mutations were found in the gyrB (gyrase gene) and parC gene encoding DNA topoisomerase IV. Conclusion: The results of this study indicate that mutations in the gyrA (gyrase gene) are a significant mechanism of resistance to fluoroquinolones. Identifying these mutations can aid in the detection of fluoroquinolone-resistant isolates and simplify treatment challenges by selecting the appropriate antibiotic.

Keywords:

antibiotic resistance , ciprofloxacin , QRDR mutation , Pseudomonas aeruginosa