Estudo sobre a ação de óleos essenciais no controle de microganismos causadores de mastite bovina

Abstract

Bovine mastitis is one of the main diseases that affect dairy cattle in the world. It consists of inflammation of the mammary gland, caused mainly by some bacterias. The economic impacts associated with this disease led to a decrease in milk production and quality, discart of milk, expenses with medicines, veterinary services and premature losses of animals. In general, the treatment and prevention of bovine mastitis is done through the use of antimicrobials. However, the exacerbated use of these drugs, often in an empirical and subtherapeutic manner, is contributing to the increase in antimicrobial resistance in mastitis pathogens. Searches for alternative treatments are required and essential oils are presented as promising possibilities due to their natural origin and well-reported antimicrobial activity. Thus, the objective of this study was to isolate, identify and determine the antimicrobial susceptibility profile of bacteria that cause bovine mastitis in municipalities in the Serra Gaúcha region, Rio Grande do Sul, to evaluate the presence of the mecA gene and its mecC homologue in the isolates belonging to the genus Staphylococcus, in addition to analyzing the antibacterial activity of essential oils of lemon grass, thyme, lavender, eucalyptus and mint on these isolates. In all, 41 microorganisms were identified. The group of Staphylococcus coagulase-negative was the most prevalent (65.8%), followed by S. aureus (17.1%). High percentages of resistance to penicillin (39.02%) and tetracycline (34.14%) were detected, in addition to high percentages of multidrug resistance. Regarding essential oils, lemongrass oil proved to be more efficient over all tested microorganisms, while eucalyptus oil showed little promising results. The results found in this work show high resistance to antimicrobials in microorganisms that cause bovine mastitis in counties belonging to Serra Gaúcha and suggest that oils of lemongrass and thyme may be an alternative for the treatment in substitution to conventional drugs. However, studies on the cytotoxicity, stability and form of application of these plant derivatives are still needed.