Prevalence, Antibiotic Resistance Pattern, Screening of psm A and psm B Gene Expression, and in Vitro Analysis of Biofilm Formation of Staphylococcus aureus Isolated from Clinical Samples

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.

Keywords:

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