Inhibitory effect of 14 essential oils against resistant pathogenic bacteria and fungi and chemical compositions of selected essential oils

Current antimicrobial agents have become useless against multidrug-resistant pathogens. There is a necessity to discover novel antimicrobial compounds to combat these pathogens. The global trend promotes a greener and more sustainable alternative, such as essential oils (EOs). EOs are complex volatile bioactive compounds, which assist plants in the defense against pests and pathogens. A total of 14 EOs were tested for antibacterial and antifungal activity against resistant pathogens. The thyme EO completely inhibits the plant pathogenic fungi at all concentrations (100% inhibition), followed by cinnamon which completely inhibits all plant pathogens at 500 and 1, 000 μl/l concentration (100% inhibition). While lemongrass was the most active EO against all bacteria except for Enterococcus caecium, it had the highest zone of inhibition (22 mm) against Mannheimia haemolytica. Tea tree was the second active EO. Thyme was the most sensitive EO against all pathogenic bacteria except for Listeria monocytogenes (ATCC 19115) and Salmonella enterica. In conclusion, there is strong evidence that EOs provide a suitable sustainable alternative to conventional therapeutic agents, which could decrease the minimum effective dose of the drugs, thus reducing their possible adverse effects and the costs of treatment.