Introduction: Staphylococcus aureus is a major causative agent of nosocomial infections which produces a wide range of diseases due to biofilm formation. This study aimed to investigate the phytochemical composition of Helichrysum artemisioides extract, its anti-biofilm effects on clinical isolates of ­methicillin-resistant Staphylococcus aureus, as well as, analysis of icaD gene expression.

Materials & methods: First, the phytochemical composition of H. artemisioides extract was studied by GC/MS method. Then, the biofilm formation capacity of 50 clinical isolates of S. aureus was evaluated by Congo red agar and polymerase chain reaction (PCR). Finally, after treatment of strains with SubMIC ­concentration of the extract within 24 hours, the expression level of icaD gene was evaluated by Real Time PCR.

Findings: The phytochemical analysis of extract showed 52 compounds, including α-Pinene (12.5%) and Carvacrol (8.6%) as the major components. The evaluation of biofilm formation test shows that out of 50 strains of S. aureus, 10 strains (20%) were positive for biofilms formation. Also, after treatment of selected strains by SubMIC concentration of the extract, the gene expression quantitation of icaD was down-regulated significantly (P<0.05).

Discusion & conclusions: Due to the significant effects of H. artemisioides extract on biofilm formation, it seems that the extract could be used as complementary therapy to inhibit S. aureus biofilm.