No abstract

Cell-to-cell communication or quorum sensing (QS) leads to biofilm formation and causing other virulence factors which are extreme problems for food safety, biofilm related infectious diseases etc. This study evaluated the anti-QS activity of the extract (0.5-4 mg/ml) by using a biosensor strain and biofilm formation by crystal violate assay. Experimental results demonstrated that the overall yield of extract was 11.33 ± 0.3% (w/w). MIC for (Gram positive), Typhimurium (Gram negative) was 1, 2 and 2 mg/ml, respectively. A concentration of 4 mg/ml extract showed highest biofilm inhibition 51.96% on Typhimurium when 47.06%, 45.28% were shown by, respectively The damage of biofilm architecture was observed by Confocal Laser Scanning Microscopy (CLSM). A level of 44.59% inhibition of violacein production was demonstrated when the dose was 4 mg/ml. Swarming motility inhibition was observed in a dose dependent manner. Taken together, the treatment of extract can deliver value to food product and medicine by controlling pathogenesis.

The aim of the present study was to evaluate the quorum sensing (QS) inhibition potential of eugenol and eugenol nanoemulsion against QS-dependent virulence factor production and gene expression, as well as biofilm formation in Pseudomonas aeruginosa. In the current study, eugenol nanoemulsion at a sub-MIC of 0.2 mg/mL specifically inhibited about 50% of the QS-mediated violacein production in Chromobacterium violaceum, as well as the production of N-(3-oxododecanoyl)-l-homoserine lactone (3-oxo-C12-HSL) and C4-HSL N-acyl homoserine lactone signal molecules, pyocyanin, and swarming motility in P. aeruginosa. The inhibitive effect of eugenol and its nanoemulsion on the expression of the QS synthase genes was concentration dependent, displaying 65 and 52% expression level for lasI, respectively, and 61 and 45% expression level for rhlI, respectively, at a concentration of 0.2 mg/mL. In addition, the inhibitive effect of eugenol and its nanoemulsion on the expression of the rhlA gene responsible for the production of rhamnolipid was also concentration dependent, displaying 65 and 51% expression level for the rhlA gene, respectively, at a concentration of 0.2 mg/mL. Eugenol and its nanoemulsion also displayed 36 and 63% respective inhibition of biofilm formation by P. aeruginosa at the 0.2 mg/mL concentration. Therefore, the nanoemulsion could be used as a novel QS-based antibacterial and antibiofilm agent for the control of harmful bacteria.