Antimicrobial activity of several essential oils on pathogenic and beneficial bacteria

The possibility to transfer antibiotic resistance from animal gut bacteria to human pathogens by animal source foods has stimulated the search for alternatives to replace the antibiotic use on animal production. Essential oils (EOs) and beneficial bacteria have been considered as alternatives. This study evaluated, in vitro, the antibacterial activity of EOs, individually and in binary blends, on pathogenic and beneficial bacteria that can occur in the swine and poultry gut. An initial screening was made with 28 EOs to verify their antibacterial activity on a model pathogenic bacterium Salmonella Enteritidis and a model probiotic bacteria Lactobacillus plantarum. The EOs from leaves of Eucalyptus globulus, E. exserta, Pimenta pseudocaryophylllus, and also two EOs, named Orange Oil Phase Essence, and Citrus Terpens, which are by-products of orange juice production, presented the greatest activity on pathogenic bacterium (S. Enteritidis) and the lowest activity on beneficial bacterium (L. plantarum). These five EOs were tested additionally, alone and in binary blends, against other four pathogenic bacteria: Staphylococcus aureus, Escherichia coli, Enterococcus faecalis and Listeria innocua, and against other two beneficial bacteria: Lactobacillus rhamnosus and Bacillus subtilis. Orange Oil Phase Essence and Citrus Terpens were oils that showed the greatest activity on pathogenic bacteria and the lowest activity on beneficial bacteria (p < 0.05), therefore presenting the best selective antibacterial activity between both groups of bacteria. The possibility of having a new usage for citrus EOs, which are by-products of the food industry, represents important information.