Pseudomonas aeruginosa is among the best known hospital pathogens. This organism is the most common
opportunistic pathogen with an innate resistance to many antibiotics. Its inborn resistance to many antimicrobial
agents and its ability to develop multidrug resistance imposes a serious therapeutic issue. Resistance of this
bacterium against different antibiotics has been reported from various regions. The purpose of this study was to
clarify the presence of resistance genes to ESBL antibiotics in Pseudomonas aeruginosa strains isolated from
different parts of Tonekabon Shahid Rajai hospital in North of Iran using PCR technique. In this study, 35 strains of
Pseudomonas aeruginosa were collected from different wards of Tonekabon Shahid Rajai Hospital within 2011-
2012. To determine the resistance of strains, antibiogram test was performed by the disk diffusion method. Specific
primers were used to detect the presence of the studied genes, and the PCR technique was applied to amplify the
above genes. the strains showed different levels of resistance to antibiotics including, 42.8% to Tobramycin, 20% to
Ceftazidime, and 2.8% to Imipenem. All Pseudomonas aeruginosa isolates did not show any resistance to
Ciprofloxacin and Amikacin. Of total 35 studied strains, PstS, and blaoxa -50 genes were observed, in 35 (100%) and
34 (97.1%) strains, respectively. Regarding the high percentage of resistance of isolated Pseudomonas aeruginosa
to the antibiotics of the ESBL, the accurate performance of antibiogram tests before the prescription of antibiotics
seems to be an unavoidable necessity in the treatment of infections resulted from these bacteria. This study is the
first report of presence of PstS and blaOXA type genes in P. aeruginosa isolates, in Tonekabon Shahid Rajai
hospital in North of Iran
