LAUSR

BACKGROUND Nowadays, novel antimicrobial strategies are being developed which focus on debilitating, rather than killing the microorganisms. In this regard, anti-biofilm therapy is one of the important ways to combat bacterial infections. Therefore, the aim of the current study was to evaluate the anti-biofilm activity of Carvacrol against E. faecalis by means of its effects on biofilm formation as well as on the gene expression levels of the two biofilm related genes, Epa and Esp. METHODS A total of 40 clinical strains of E. faecalis were collected from three hospitals in Tehran, Iran during 2020. These isolates were confirmed by biochemical and genotypic methods. Antibacterial and anti-biofilm activity of Carvacrol essence were determined according the standard protocol. Finally, expression level of the biofilm related genes (Epa and Esp) were evaluated before and after the treatment with Carvacrol. RESULTS A total of 14 isolates were considered as strong biofilm producers and were used for analysis. Carvacrol essence showed the best antibacterial activity at 2,500 μg/mL concentration against all the isolates, the biofilm formation capacity was decreased by Carvacrol essence, and it was statistically significant (p < 0.05). Expression levels of the Esp gene were decreased in 5 isolates while increased in 3 isolates following the Carvacrol treatment. Ex-pression levels of the EpaI gene was significantly decreased (p < 0.05) in 4 isolates following the Carvacrol treatment. CONCLUSIONS In conclusion, the results presented in this study suggest that carvacrol extract exhibits significant antimicrobial and anti-biofilm properties against E. faecalis, even against vancomycin resistant isolates.