In vitro activity of essential oils against gram-positive and gram-negative clinical isolates, including carbapenem-resistant enterobacteriaceae

Background. There is increasing demand for compounds to treat antimicrobial-resistant pathogens, and essential oils have gained interest. Moreover, previous studies have demonstrated antimicrobial activity of these nonpharmaceutical products. We investigated the activity of essential oils against multiresistant bacteria and other clinical isolates to evaluate the potential of their use topically and/or internally for treatment of bacterial infections. Methods. We studied the in vitro activity of 10 essential oils and 1 essential oil blend against clinical isolates including extended-spectrum beta-lactamase-producing Enterobacteriaceae, carbapenem-resistant Enterobacteriaceae, multidrug-resistant Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus. Results. Essential oils of oregano, thyme, cinnamon bark, and lemongrass had the largest zones of inhibition against Gram-positive organisms, whereas cinnamon bark had the largest zone of inhibition against P aeruginosa. Oregano, thyme, and cinnamon bark had the largest zones of inhibition against Enterobacteriaceae. Conclusions. Essential oils have promising in vitro activity that warrants further study of their activity and use in the clinical setting.