Determination of Antibacterial Activity of Essential Oils from Aromatic Plants Against Pathogenic and Antibiotic Resistant Microorganisms in Animals and Animal Products

Dairy calf mastitis is a relatively common infectious condition that mostly results from Staphylococcus aureus infections. It causes significant economic losses for dairy farmers all over the world. Due to the misuse of drugs, drug-resistant pathogens have started to emerge. Since these pathogens do not respond to commonly used treatments, the economic loss is increasing every year. In this study, the antimicrobial activity of three different plants (Origanum onites, Teucrium polium and Vitex agnus-castus) collected from Aydın and its surroundings on six different antibiotic-resistant microorganisms some of which are the causative agents of mastitis, was determined using agar disc diffusion methods. The essential oil of O. onites had 32 mm inhibition zone against MRSA, while the antibiotic used as standard had no effect. The essential oil of T. polium showed the smallest inhibition zone (3 mm) against MRSA and the biggest inhibition zones (20.5 mm) against Pseudomonas aeruginosa. Extracts of V. agnus-castus formed zones of inhibition against Bacillus cereus CCM99 and Staphylococcus aureus ATCC 6538 of 23.5 and 36 mm, respectively. In addition, comparing the data of this study with literature data, it is suggested that β-farnesene in T. polium, carvacrol and o-cymene in O. onites and 1,8-cineole in V. agnus-cactus L. may be more effective in antibacterial activity than other essential oil constituents. This study has shown that the essential oils of these plants could be important components of drugs that can be employed against multidrug-resistant pathogens that cause disease in humans and animals, many of which are foodborne.