Davood Azadi - Molecular and medicine research center, Khomein University of Medical Sciences, Khomein, Iran
Pegah Khandan Del - Department of Microbiology, Gorgan Branch, Islamic Azad University, Gorgan, Iran
Mohammad Shafiee - Stem cell Research Center, Golestan University of Medical Sciences, Gorgan, Iran
Ali Asghar Ayatollahi - Medical Laboratory Sciences Research Center, Golestan University of Medical Sciences, Gorgan, Iran
Ania Ahani Azari - Department of Microbiology, Gorgan Branch, Islamic Azad University, Gorgan, Iran
Abolfazl Khandan Del - Infectious Diseases Research Center, Golestan University of Medical Sciences, Gorgan, Iran
Mehdi Safarabadi - Molecular and medicine research center, Khomein University of Medical Sciences, Khomein, Iran

Backgrounds: Staphylococcus aureus is one of the major causes of nosocomial infections. Biofilm formation is an important virulence factor of S. aureus, leading to its high resistance to antibiotics and evasion from host defenses. This study aimed to assess the prevalence and antimicrobial resistance profile of biofilm-producing S. aureus strains and characterize genes involved in biofilm formation. Materials & Methods: A total of ۷۹ S. aureus strains were isolated from ۱۰۰۰ clinical samples and characterized using phenotypic, biochemical, and molecular tests. The biofilm production ability of isolates was examined using the microtiter assay. Moreover, the expression of genes involved in biofilm production (psm A and psm B) was screened using real-time PCR. Finally, antibiotic susceptibility testing was done using the Kirby-Bauer method and interpreted according to the CLSI M۱۰۰ standard. Findings: Out of ۷۹ S. aureus isolates, ۴۳ (۵۴.۴%) isolates were strong biofilm producers, ۲۱ (۲۶.۶%) isolates were weak biofilm producers, and ۱۵ (۱۹%) isolates were non-adhesive. The results of real-time PCR showed that ۵۵ (۸۶%), ۶۰ (۹۳.۷%), and ۴۶ (۵۸.۲%) isolates were positive for psm A, psm B, and both genes, respectively. The results of antibiotic susceptibility testing showed that all the isolates were resistant to two or more antibiotics. Conclusion: The high prevalence of biofilm-forming S. aureus strains in hospital environments could be a major health challenge with serious outcomes for hospitalized patients. Thus, it is necessary to disinfect hospital environments to reduce the risk of infection and spread of these microorganisms.

Staphylococcus aureus, Biofilm, Real-time PCR, Antibiotic susceptibility.