Background: Pseudomonas aeruginosa is an opportunistic pathogen and a major cause of nosocomial infections. The aim of this study was to evaluate the frequency and determine the antimicrobial resistance in clinical strains of Pseudomonas aeruginosa isolated from different parts of Tehran hospitals in 2013.

Methods: In this cross-sectional study, during the six-month period, 180 samples were collected from different parts of eight hospitals in Tehran using of targeted sampling of the Modal Instance type. Biochemical tests were performed to identify the species and level of antibiotic-resistant in studied isolates by Kirby-Bauer disk diffusion susceptibility test protocol. The Chi-Square test was used for statistical analysis under the IBM SPSS 22 software.

Results: The 159 isolates of Pseudomonas aeruginosa (111 males and 48 females) were identified of 180 clinical samples. Strains isolated from wound (%44/1) and urine (%29/8) had the highest frequency. Also %97.5 of strains were hemolytic and only %2.5 were non- hemolytic (gamma hemolytic). The %88 of the isolates were resistant to at least one or more of an antibiotic. The Most antibiotic resistance was observed against cefotaxime (%62.9) and Aztreonam (%60.4) and %70 of strains were multiple drug resistance (MDR).

Conclusion: In this study, Pseudomonas aeruginosa strains showed the lowest resistance to imipenem that the antibiotic may be recommended as the main treatment option. The high prevalence of multidrug resistant strains, is a serious warning.