BACKGROUND AND OBJECTIVE: The expression of most genes that produce Pseudomonas aeruginosa virulence factors is controlled and regulated by a gene system called quorum sensing (QS) system. Quorum sensing is a cell to cell communication system through small signaling molecules in single-celled organisms. This study aims to investigate the frequency of Pseudomonas aeruginosa lasB, rhlR, rhlI, lasR, lasI, apr and rhlAB genes isolated from clinical samples using multiplex-PCR method and determining the antibiotic resistance profile.

METHODS: In this cross-sectional study, 60 clinical isolates of Pseudomonas aeruginosa were collected from patients admitted to Imam Khomeini hospital in Tehran. The antibiotic susceptibility of these isolates against ceftazidime, cefotaxime, amoxicillin, ciprofloxacin, amikacin, gentamicin, imipenem, cefepime, ticarcillin and piperacillin was determined using disk diffusion method. After culturing and final confirmation using biochemical and specific tests, multiplex polymerase chain reaction (Multiplex PCR) was performed to track the intended genes.

FINDINGS: In this study, highest susceptibility was observed to be against ciprofloxacin (81.66%) and ceftazidime (65%). Multiplex PCR demonstrated that the frequency of rhlR, lasR and lasI genes was 5%, 48.3% and 60%, respectively, while rhlI, lasB, apr and rhlAB genes could not be identified in any of the strains.

CONCLUSION: Resistance to antibiotics is increasing in Pseudomonas aeruginosa, which requires continuous monitoring. QS System plays a key role in pathogenicity of Pseudomonas aeruginosa. Identification of these genes enables us to track and identify this bacterium quickly.