ROLE OF MEXZ GENE IN CIPROFLOXACIN RESISTANCE IN PSEUDOMONAS AERUGINOSA ISOLATES IN GUILAN PROVINCE

Pseudomonas aeruginosa is an opportunistic pathogen and one of mortality causes
of nosocomial infections specifically in severely burned patients. One of the drug resistant
mechanisms in pseudomonas aeruginosa is mutation in negative regulator genes of mexXY efflux pump
system. In this study, the role of mexZ mutations was investigated in ciprofloxacin resistant development
in Pseudomonas aeruginosa isolates in Guilan province.
Materials & Methods: In this study, 45 strains of pseudomonas aeruginosa isolated from different
clinical samples of Rasht and Lahijan hospitals and laboratories between 2014 to 2016 were identified
by biochemical tests. The antibiotic resistance and susceptibility of the strains were investigated by
Kirby Bauer method and MIC determination. Then PCR-sequencing was performed to assess MexZ
gene mutations in ciprofloxacin resistant strains.
Results: From 45 isolates of pseudomonas aeruginosa, all were resistant to cefixime, cephalothin and
trimethoprim; whereas 17 isolates were ciprofloxacin resistant. The highest MIC of ciprofloxacin was
determined 1024 μg/ml. Also, PCR-sequencing analysis showed that 8 isolates had missense mutations
in MexZ gene such as L111E and R143P.
Conclusion: In this study, mutation in mexZ as negative regulator of mexXY can be a reason of multidrug
resistance in some strains in Guilan province. It appears that mexZ mutation led to affinity
modification in mexZ protein binding to DNA in some isolates