The Synergic Activity of Eucalyptus Leaf Oil and Silver Nanoparticles Against Some Pathogenic Bacteria

Background: Notwithstanding the current advances in the drug discovery and the pharmaceutical biotechnology, the bacterial infectious diseases are still one of the biggest health concerns worldwide. Also, the new therapeutic methods are urgently required due to the increasing resistance to antimicrobial agents. Objectives: The current study aimed at investigating the synergic effect of eucalyptus leaf oil and silver nanoparticles (Ag NPs) on Escherichia coli H7:O157, Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA), Salmonella enterica, and Bacillus subtilis. Methods: The current experimental study was performed in Islamic Azad University, Iran. The disc diffusion method, well diffusion method, and broth dilution assay were used in the current study. Results: Results showed that none of the drugs affected the bacteria by disk diffusion method. In broth dilution method, E. coli O157:H7, E. coli, MRSA, and S. enterica showed the same susceptibility and B. subtilis showed more susceptibility to the combined agents. Conclusions: The current study showed the synergic effect of Ag NPs 1.5 ppm plus eucalyptus leaf oil on the growth inhibition of E. coli O157:H7, E. coli, MRSA, S. enteric, and B. subtilis. The combined drug showed more efficiency; lower dose of each medicine in the combinatory form decreased the toxicity in the treatment of infections caused by these bacteria.