Pseudomonas aeruginosa is one of the drug-resistant opportunistic pathogens with the ability to form biofilm and to produce a number of virulence factors via Quorum Sensing (QS) regulation. Most researchers have focused on QS inhibition to overcome the drug resistance problem. QS inhibitor molecules are investigated from natural resources. In the present study, anti-QS activities of ethyl acetate extracts of decoction and infusion samples from Helianthus annuus leaves were tested on biosensor strains of P. aeruginosa (lasB-gfp, rhlA-gfp and pqsA-gfp), as well as anti-biofilm activities on PAO1 wild type. H. annuus leaf samples were firstly infused or decocted and then extracted with ethyl acetate. The efficacies of infusion or decoction extracts were examined at the concentrations of 240, 120, and 60 μg/ml in 96-well microplates and evaluated in Citation 3 multimode microplate reader (Biotek). The inhibition rates of decoction extracts were recorded as 70.61% for las, 44.09% for rhl and 83.77% for pqs system at 240 μg/ml. The biofilm inhibition percentages of the extracts were determined to be 50.82% (±1.36). Moreover, inhibition rates for infusion extracts were detected as 62.08% for las, 45.15% for rhl and 77.79% for pqs, and 53.88% (±3.94) for biofilm formation. In conclusion, the potential efficacies of the extracts of decocted or infused H.annuus leaves were demonstrated on QS system and biofilm formation of P. aeruginosa. However, there is a need for more detailed investigations and determination of the active substances that have QSI and anti-biofilm effect.

Recently, misuse or overuse of antibiotics has led to antibiotic resistance problem, a global healthcare problem. Most virulence factors and biofilm formation in Pseudomonas aeruginosa are controlled by quorum sensing (QS). The inhibition of QS system by inhibitor molecules has been suggested as a novel alternative antivirulence approach in which no need to kill the bacteria.In the present study, QS and biofilm inhibitory potentials of the methanol and acetone extracts of Prunus avium stalk against P. aeruginosa were evaluated. The extracts were tested at the concentrations of 240, 120, and 60 μg/ml. lasB-gfp, rhlA-gfp, pqsA-gfp biosensor strains and P. aeruginosa PAO1 were used to monitor QS and biofilm inhibition, respectively. Fluorescence and absorbance measurements were performed on Cytation 3 multimode microplate reader. QS inhibition ratios for las, rhl, and pqs systems and biofilm inhibition ratios of the acetone extracts were recorded as 70.43%, 47.25%, 76.31%, and 47.76% (±6,60) and of the methanol extracts as 74.96%, 40.10%, 71.89%, and 38.54% (±3,56) at a certain concentration of 240 μg/ml, respectively. As a result, anti-QS and anti-biofilm properties of acetone extracts were better than that of methanol extracts. Further investigations are needed to discover inhibitor compounds of P. avium and also their effects on human cells and then these compounds may be used in new drug discoveries.