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INTRODUCTION: The quorum sensing (QS) systems are involved in biofilm formation ability of Pseudomonas aeruginosa, as key factors in the development of infections. Therefore, the aim of this study was to determine the frequency of significant QS encoding genes, including lasI, lasR, rhlI, and rhlR, in clinical isolates of P. aeruginosa. MATERIALS AND METHODS: This study was performed on 100 clinical isolates of P. aeruginosa that were identified by biochemical, microbiological, and PCR tests. The biofilm formation assay was done by microtiter plate method. Alkaline Lysis was used to extract the genomic DNAs. Then, the PCR method was used to identify the 16 S rRNA gene and the frequency of the lasR, lasI, rhlR, and rhlI genes. RESULTS: Among 89 biofilm-producer isolates, 48 (53.93%), 17 (19.1%), and 24 (26.96%) showed a strong, moderate, and weak biofilm formation ability, respectively. The lasI gene was identified in 94% of the isolates and the rhlR gene was presented in 99% of the isolates, while 100% of the isolates carried the lasR and rhlI genes. Among the 6 isolates lacking the lasI gene, 3, 1, 1, and 1 isolates were collected from the ICU, emergency, burn, and surgical departments, respectively. In addition, 3, 1, 1, and 1 isolates lacking the lasI gene were collected from sputum, urine, wound, and catheter samples, respectively. One strain lacking the rhlR gene was also isolated from a wound sample in burn department. In this study, 94% of the isolates had all 4 genes tested, while 100% of the isolates carried at least 3 QS genes. CONCLUSION: Considering that all biofilm-producing isolates were collected from hospitalized patients with active infections, it can be concluded that the presence of QS genes in the development of acute infections caused by this organism has been proven in this study.
Aghamahali et al. (Tue,) studied this question.