Study of Antibacterial Synergistic Effect of Origanum vulgare L. Essential Oil andSilver Nanoparticles

The increasing use of antibiotics and the prevalence of resistant strains have necessitated the use of new antimicrobial drugs. Combination therapy is an effective strategy to combat antibacterial resistance. The aim of this study was to investigate the antibacterial synergistic effect of Origanum vulgare essential oil and silver nanoparticles on gram-positive and gram-negative bacteria. In this study, O. vulgare essential oil was extracted from the plant branch. A colloidal solution of silver nanoparticles with an average particle diameter of 68 nm was purchased. The antibacterial effect of O. vulgare essential oil and silver nanoparticles was investigated alone and then in combination by broth microdilution method and their minimum inhibitory concentration (MIC) against gram-positive and gram-negative bacteria was determined. The bacteria studied were Escherichia coli, Salmonella enterica, Bacillus subtilis and Staphylococcus aureus. Based on the obtained results, the synergistic effect of O. vulgare essential oil and silver nanoparticles had significant antimicrobial effects on all studied bacteria. The results showed that the synergistic effect of O. vulgare essential oil and silver nanoparticles was effective in inhibiting and killing the studied bacteria. And they can be useful in developing new drugs against these bacteria.