Background: Pseudomonas aeruginosa is a major nosocomial pathogen that due to its intrinsic and acquired resistance to a wide spectrum of antibiotics poses a threat in clinical settings. One of the drug resistance mechanisms in P. aeruginosa is mutation in negative regulators of efflux pump systems such as nalC. The aim of this study was investigation of nalC mutations in P. aeruginosa isolates from some Rasht hospitals and Lahijan laboratories.  

Materials and Methods: In this cross-sectional study, forty-five P. aeruginosa strains was isolated from several Rasht hospitals and Lahijan laboratories between 2013 to 2014 and identified by biochemical tests. The antibiotic resistance and susceptibility of isolates was determined by Kirby Bauer method and microdilution method. Then PCR-sequencing was carried out to assess nalC mutations in ciprofloxacin resistant isolates.

Results: In this study, the most P. aeruginosa strains was isolated from urine sample (53%), followed by burned strains (31%). The most resistance was seen to erythromycin (100%) and the lowest resistance was seen to ciprofloxacin (~31 %). The highest MIC of ciprofloxacin was determined in some strains >512 μg/ml. Sequencing results showed that 12 ciprofloxacin resistant isolates had one or several missense mutations G71E, S209R and  E153Q in nalC gene.

Conclusion: Given that mutation was defined in most isolates in this study, it seems that mutation in nalC gene plays an important role in ciprofloxacin resistance of nosocomial P. aeruginosa isolates in Guilan province.