ساناز ده باشی - Dept. of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
حامد طهماسبی - Dept. of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
بهروز زینی - Dept. of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
محمدرضا عربستانی - Dept. of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran

Background and Objective: Quorum sensing (QS) phenomenon, promoters involved in this pathway and the effect of these promoters on the expression of some structural genes, such as agrA and PII, could reveal the proper activity and gene expression of antibiotic resistance in S. aureus. The aim of this study was defining the relationship between promoter-dependent Quorum Sensing induced genes and methicillin resistance in clinical strains of S. aureus. Materials and Methods: In this analytical study, ۳۱۵ isolates of S. aureus were collected. Resistant and susceptible strains were evaluated for the presence of promoter-dependent quorum sensing induced genes qualitatively and quantitatively. Calculating the gene expression of agrA and PII was carried out by Real-Time PCR. Statistical analysis (descriptive and analytical) was done using SPSS version ۱۶ software and the data analysis of gene expression was carried out by REST ۲۰۰۸ V۳. Results: Among ۱۲۵ strains of S. aureus resistant to methicillin, ۱۰۰ isolates (۸۳/۳۳%) had the promoter P۲ gene and all isolates had the agrA gene and of ۱۹۰ strains susceptible to methicillin, ۸۴ isolates (۴۴/۲۱%) had the P۲ gene and ۱۶۹ isolated (۸۸/۹۴%) had the agrA gene. P۲ and AgrA gene expression was greater in the resistant isolates in comparison to susceptible isolates. Conclusion: In accordance with the results of this study, the association between quorum sensing /gene induction and drug resistance is a matter of importance.

Keywords: Quorum sensing, Drug resistance, Staphylococcus aureus, Gene expression