Background and Objectives: Detection of TEM and SHV genes in ESBL producing Pseudomonas aeruginosa and their antimicrobial resistance pattern can provide useful information about the epidemiology and risk factors of associated infections. In this study we determined the antimicrobial susceptibility pattern and prevalence of ESBLs in clinical isolates of Pseudomonas aeruginosa by phenotypic and genotypic methods.

  Methods: In this analytic-descriptive study, 110 Pseudomonas aeruginosa strains isolated from different clinical specimens were used. The pattern of antimicrobial resistance was determined by disk diffusion (Kirby-buer) method. The ESBL production was determined by combination disk method using disks containing ceftazidim and cefotaxim alone and in combination with Clavulanic acid. SHV and TEM types of ESBL producing genes was detected by PCR. 

  Results: In this study Co-trimoxazole and Amoxicilin with 96.4% and 92.7% and Amikacin with 17.3% showed the highest and lowest resistance against isolates respectively. According to PCR results 37.5% and 12.5% of isolate were carried SHV and TEM genes respectively and 12.5% of isolate were carried both the SHV and TEM genes.

  Conclusion: According to the results most of the isolates are drug resistant and among the ESBL producing strains the frequency of SHV type is higher than TEM . The isolate ceftazidim resistance was contains SHV (37.5%) and TEM gene (12.5%), that showed SHV and TEM genes play more important role in create of ceftazidim resistance than cefotaxim resistance.