Introduction: Pseudomonas aeruginosa is a major agent of hospital infection which has a resistance intrinsic to a wide range of Antibiotics. It is resistant to beta-lactam antibiotics because of Beta-lactamase and Metalo-lactamase enzymes production. They have crucial problems in the treatment. The goal of this research is to isolate and characterize strains which are resistant to beta-lactam and Imipenem Antibiotics in clinical samples from four major hospitals in Tehran.

Methods & methods:  In this study 600 samples of Pseudomonas aeruginosa were  collected  from patients and those people  referring to Baqyiatallah hospital ,  Imam Khomeini hospital , Shahid Motahari Burns Center and Pediatrics Center during two years, In the first step Antibacterial resistance were prefer by wide range of Antibiotics (Kirby-Bauar). The MIC test was used to Ceftazidime and Imipenem by Microdiution tube and  CLSI protocol.

Findings: This research demonstrated that the highest sensitivity of bacteria is to Imipenem (92%) and Tetracycline (91.2%) The results showed that 6 % of the MIC of strains are resistant to imipenem (4μg/ml≤ MIC) and the 39/5 % of them are resistant to Ceftazidime (16μg/ml ≤ MIC), respectively.

Discussion & conclusions: These results showed that consumption of these Antibiotics should be used precisely due to the highest resistance of these bacteria to Imipenem and third generation Cephalosporin’s otherwise it can transfer to other strains Gram-Negative bacteria special.