In vitro effects of cinnamon, oregano, and thyme essential oils against Escherichia coli and Trueperella pyogenes isolated from dairy cows with clinical endometritis.

Clinical endometritis causes serious economic losses in dairy farms, mainly due to its negative health impact on fertility and milk production, as well as the additional costs of medicines used to treat the affected animals. The therapy for uterine diseases is principally performed with antibiotic treatment; however, its indiscriminate use in dairy herds can favor the increase in the resistance of pathogenic bacteria, leading to treatment failures. In this regard, the use of unconventional treatment may be a good option to reduce the use of antimicrobials in milk production. The objective of the present study was to evaluate the antibacterial activity of cinnamon, oregano, and thyme essential oils, and their combinations, against bovine uterine pathogens. The antibacterial activities of these essential oils were evaluated by the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC), and Fractional Inhibitory Concentration (FIC) indices against Escherichia coli and Trueperella pyogenes, which were isolated from dairy cows with clinical endometritis. Among the essential oils evaluated, the lowest MIC and MBC values observed were obtained with cinnamon essential oil alone. The association among essential oils showed different kinds of interactions, and in some situations, antagonism was observed. This study demonstrated a promising antimicrobial activity of cinnamon's essential oil, indicating that it has excellent potential to be explored as a possible alternative in the treatment of clinical endometritis in dairy cows.