Abstract

Many opportunistic pathogenic bacteria use the Quorum Sensing (QS) system to coordinate their virulence expressions. Thus, QS can likely be a new approach to control bacterial infections. The aim of this study was to evaluate the antimicrobial, anti-biofilm, and anti-quorum sensing activities of ethanol, chloroform, and dichloromethane: methanol extracts of leaf, stem, and fruits of the European mistletoe Viscum album L. on 2 Gram-positive and 7 Gram-negative pathogenic bacteria. The extracts at concentrations ranging from 50 to 250mg/ml were tested depending on the extracts of the plant parts and the test bacteria. The extract with 50mg/ml concentration, in which no antimicrobial activity was observed, was used for anti-quorum sensing and antibiofilm studies. The dichloromethane: methanol extracts were found to show the highest biological activities. QS activities of the plant extracts were also determined using the recently established Chromobacterium violaceum CV026 reporter strain and the signaling molecule N-(ß-ketocaproyl)-L-homoserine lactone (3-oxo-C6-HSL) agar well diffusion assay. Biofilm was quantified using the microtiter plate test and the crystal violet assay. Anti-microbial, anti-biofilm, and anti-quorum sensing activity of leaf and stem extracts showed higher efficiency than fruit extracts. It was concluded that the extracts of V. album had the potential to treat microbial infections by biofilm inhibition or inhibition of QS.