In vitro antimicrobial effect of essential tea tree oil(Melaleuca alternifolia), thymol, and carvacrol on microorganisms isolated from cases of bovine clinical mastitis

Abstract

Both Gram-negative and Gram-positive bacteria have recently developed antibiotic resistance to treatments for bovine mastitis, creating a serious concern for public and animal health. The objective of this study was to analyse in vitro microbicidal activity of tea tree oil, thymol and carvacrol (composed of oregano and thyme essential oils) on bacteria isolated from clinical mastitis. Field isolates and ATCC strains of the Staphylococcus spp, Streptococcus spp, Escherichia coli, Klebsiella pneumoniae, and Candida albicans genera were analysed. The agar diffusion technique was used to test bactericidal susceptibility and plate microdilution was utilized to determine the minimum inhibitory, bactericidal, and fractional inhibitory concentrations. Thymol alone and the combinations of thymol-carvacrol and thymol-TTO obtained the highest inhibition diameters for Gram-negative bacteria, while for Gram-positive bacteria and C. albicans , thymol and the combination thymol-carvacrol obtained the highest indices. TTO, thymol, and carvacrol had MIC values of 1.56–25 mg/ml, 0.05–0.4 mg/ml, and 0.02–0.2 mg/ml, respectively. CMB results for the Gram-negative and gram-positive groups were 0.39–0.78 mg/ml, and for C. albicans , 0.78–1.56 mg/ml. Results for the fractional inhibitory concentrations show that the TTO+thymol and thymol+carvacrol combinations had additive activity against groups of Gram-negative bacteria and C. albicans . These natural components, evaluated individually and in combinations, have an effectiveness above 70%.

Plant Essential Oils as a Tool in the Control of Bovine Mastitis: An Update

“…Scanning electron microscope revealed that cells exposed to CAR + OA show severe morphological changes and disruption of cell wall and cell membrane, which results in the release of inner cell material into the surrounding environment. The results on the antimicrobial activity of carvacrol are confirmed by Corona-Gómez et al [75].…”

“…Its interaction with the membrane affects the permeability and results in the release of ATP and K + ions [106]. Based on its MIC (0.05-0.9 mg/mL), MBC (0.2-1.9 mg/mL), and zone of inhibition (13.5-43.8 mm), thymol is highly effective against isolates from mastitis cows [74][75][76]97]. These studies confirm the importance of thymol within the essential oils for the antibacterial properties of the genus Thymus.…”

“…The presence of different aromatic, phenolic, and flavonoid compounds are also considered the main reason for the significant antioxidant potential of these plants [99]. Thymol and carvacrol exhibited additive interactions against Gram-negative bacteria and C. albicans [75], while the combination with tilmicosin had an addictive effect against Staphylococcus spp., Streptococcus spp., and E. coli [97].…”

“…Tea tree oil showed bactericidal activity against Staphylococcus spp., Streptococcus spp., Escherichia coli, Klebsiella pneumoniae, and Candida albicans [75], as well as the algae Prototheca zopfii, P. wickerhamii [87].…”

Alternatives to Antimicrobial Treatment in Bovine Mastitis Therapy: A Review

“…Due to antimicrobial and antibiofilm activities [ 109 ] EOs are being considered as a subject of interest to the scientific community in the development of novel therapeutic options. The antimicrobial activity of several different EOs on common bovine mastitis pathogens was the subject of research in different in vitro studies [ 105 , 110 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 ], while some authors focused on their antibiofilm effect [ 118 , 119 , 120 ].…”