Assessment of point mutations associated with ciprofloxacin resistance in Pseudomonas aeruginosa isolates in Guilan province

Pseudomonas aeruginosa is an opportunistic pathogen especially in immunocompromised patients. Drug resistance in P. aeruginosa is caused by different mechanisms such as mutations in topoisomerases subunits and negative regulators of efflux pump systems. This study was aimed to investigate mutations in gyrB, parC, and nfxB genes in ciprofloxacin-resistant P.aeruginosa isolates in Guilan province.
In this cross-sectional study, 200 isolates were obtained from different clinical samples of Rasht and Lahijan hospitals and laboratories and subsequently identified by biochemical tests. Antibiotic susceptibility pattern was determined by Kirby Bauer disk diffusion susceptibility test and Minimum Inhibitory Concentration (MIC) test. PCR-sequencing was used to assess mutations in gyrB, parC, and nfxB genes in ciprofloxacin-resistant P. aeruginosa isolates.
Out of 69 P. aeruginosa isolates, 26 isolates were ciprofloxacin-resistant. MIC of ciprofloxacin in resistant isolates was determined between 32-1024 µg/ml. PCR-sequencing analysis revealed that some resistant isolates have missense mutations in gyrB, parC, and nfxB genes. It seems that N368S, I424L, L464I, E468D, M520L, and I524V mutations in gyrB were reported for the first time in Iran.
It seems that reported mutations in gyrB and parC genes affect topoisomerases affinity to ciprofloxacin in resistant isolates. Furthermore, mutations in the nfxB gene may lead to overexpression of MexCD-OprJ efflux pump and ciprofloxacin resistance.