Synergistic antibaterial activity of medicinal plants essential oils with biogenic silver nanoparticles

Abstract

Objective(s): Development of a nanobiosystem by using plant essential oils with green synthesized silver<br><br>nanoparticles that present synergistic antibacterial activity for overcoming antibiotic resistance in pathogenic<br><br>bacteria.<br><br>Material and Methods: Essential oils (EOs) of Kelussia odoratissima and Teucrium polium extracted by<br><br>hydrodistillation were analyzed by gas chromatography-mass spectrometry (GC-MS). Then leaf aqueous<br><br>extract of K. odoratissima prepared and used for green synthesise of silver nanoparticles (SNPs). The oils,<br><br>and the colloidal preparations of silver nanoparticles, were then subjected to microdilution technique using<br><br>ELISA reader to determine their minimum inhibitory concentration (MIC) and minimum bactericidal<br><br>concentration (MBC) on Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Escherichia coli<br><br>O157: H7, Salmonella enterica and Pseudomonas aeruginosa. The type of interaction between EO and SNPs<br><br>was also determined by calculating the fractional inhibitory concentration index and isibologram type.<br><br>Results: GC-MS analysis of K. odoratissima EO showed (Z)-ligustilide, (Z)-3-butylidene-phthalide,<br><br>limonene and β-phellandren as main constiuents, while T. polium EO has β-caryophylene, germacrene D,<br><br>γ-cadinene, (Z)-nerolidol, camphor, β-pinene, α- camphene, linalool and α-humulene. T. polium EO has<br><br>more potent antibacterial property at MIC of 0.16-1.25 mg/ml compared to K. odoratissima (MIC of 0.3-2.5<br><br>mg/ml). Silver nanoparticles showed a potent antibacterial property (MIC of 0.006-0.025 mg/ml), and its<br><br>colloidal suspension with plant EOs revealed a pathogen-dependent synergistic and additive effect based on<br><br>calculated fractional inhibitory concentration index (FICi).