Mehdi Rahimi Hezarvand - Department of Biology, Zarghan Azad University, Zarghan, Iran.
Maryam homayoon - Department of Biology, Zand Institute of Higher Education, Shiraz, Iran.

Background and Aim : Pseudomonas aeruginosa is one of the most frequent Gram-negativepathogens responsible for nosocomial infections. One of the problems in treating patients infectedwith this bacterium is the development of antibiotic resistance by various mechanisms. Mex effluxpumps play a key role in the development of multiple resistance to antimicrobial drugs. The aimof this study was to investigate the pattern of antibiotic resistance and determine the frequency ofgenes encoding Mex AB, Opr M efflux pump in isolated strains in Shiraz.Methods : In this study, in order to determine antibiotic resistance and the frequency of genesencoding the efflux pump, ۸۱ samples of Pseudomonas aeruginosa were collected from clinicalcenters in Shiraz and diagnostic tests were performed to confirm bacterial identity. To evaluate theantibiotic susceptibility, the agar disk diffusion test was used by Kirby-Bayer method accordingto the standard (CLSI). Identification of MexAB-OprM efflux pump genes was performed usingPCRResults : According to the results, MexD and OprJ genes have the lowest resistance with ۶۴% andOprM gene has the highest resistance with ۹۶%. Also, the diameter of the growth inhibition zoneby antibiotics obtained from antibiotic resistance by NCCLS method showed that these bacteriaare resistant to all antibiotics studied. Also, the resistance of Meropenem (۱۰۰%), Ceftazidime(۱۰۰%) and Ceftizoxime (۱۰۰%) was higher among all antibiotics and the lowest resistance wasrelated to Cefepime (۱۴%), also Ciprofloxacin (۸%) antibiotic is sensitive.Conclusion : The results of this study indicate an increasing antibiotic resistance amongPseudomonas aeruginosa strains. Increased expression of MexAB-OprM efflux pump genes is oneof the common mechanisms in the resistance of Pseudomonas aeruginosa isolates to antibiotics.Identifying resistance mechanisms can be useful in controlling and treating such resistant strains.

Pseudomonas aeruginosa, Antimicrobial resistance, Efflux pump, Resistance genes,PCR