Antibacterial, anti-biofilm and anti-quorum sensing activities of Artemisia dracunculus essential oil (EO): a study against Salmonella enterica serovar Typhimurium and Staphylococcus aureus

The study evaluates the effect of Artemisia dracunculus essential oil (EO) on two pathogenic bacteria Salmonella enterica serovar Typhimurium and Staphylococcus aureus and Vero cell line. To evaluating the anti-biofilm potential of the EO, a microtiter-plate test (MtP) and scanning electron microscopy (SEM) were performed. The quorum-sensing inhibitory properties were examined by QS-related gene expression at sub-MIC concentrations of Artemisia dracunculus EO. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a tetrazole) test was used to determine the cytotoxicity potential of the EO against the Vero cell line and finally, the major components of the EOs were determined using Gas chromatography–mass spectrometry (GC–MS) analysis. The minimum inhibitory concentration (MIC) of the tested EO against S. Typhimurium and S. aureus were 2.5 and 1.25 μl/ml, respectively. In addition, the minimum bactericidal concentration was 5 and 2.5 μl/ml for S. Typhimurium and S. aureus, respectively. Both MtP and SEM showed an acceptable inhibitory and disruption effect of the EO on the biofilm formation at Sub-MIC concentrations. Significant downregulation of luxS, pfs, and hld genes by treatment with MIC/2 concentration of A. dracunculus EO was observed. The IC50 value of A. dracunculus EO against Vero cells was 20 μl/ml. The main detected compound using GC–MS was estragole (methyl chavicol or tarragon) (64.94%). Anti-biofilm, QSI activity, and non-toxicity of A. dracunculus EO reported for the first time in this study propose the use of these plant compounds as alternatives to antibiotics and chemical additives.