Abstract
Bovine mastitis is the most widespread and economically important disease worldwide. The present study aimed to determine bioactive compounds in two essential oils (EOs) from wild (Thymus serpyllum) and common thyme (Thymus vulgaris) and to assess the antioxidant potential as well as antibacterial efficacy of the EOs against mastitis-associated bacteria. The study also included antibiotic susceptibility tests. The strains were previously isolated from lactating animals with clinical and subclinical mastitis. The antioxidant potential of the commercial EOs of wild and common thyme was evaluated by five in vitro assays. The antibacterial activity was performed using the microdilution technique, while antibiotic susceptibility testing was performed by the Kirby–Bauer disc diffusion method. The dominant compound in wild thyme was thymol (45.22%), followed by p-cymene (23.83%) and γ-terpinene (3.12%), while in common thyme, it was thymol (54.17%), followed by γ-terpinene (22.18%) and p-cymene (16.66%). Among the fourteen mastitis-associated bacteria, strain IX Streptococcus spp. (β-hemolytic) was the most sensitive to the tested EOs (minimum inhibitory concentration (MIC)/minimal bactericidal concentration (MBC) were 0.78/1.56 and 0.39/0.78 mg/mL for T. serpyllum (TS) and T. vulgaris (TV), respectively). Regarding Streptococcus spp. β heamoliticus, MICs for TS ranged from 0.78 to 1.56 mg/mL, while for the same oil, MBCs ranged from 1.56 to 12.5 mg/mL. In the case of T. vulgaris, MICs ranged from 0.39 to 3.125 mg/ mL, while MBCs ranged from 3.125 to 6.25 mg/mL. TV is more active against E. coli, E. sakazakii, and Streptococcus spp., while it is less effective against Staphylococcus spp. than TS. The study revealed that the tested EOs possess remarkable antioxidative and antibacterial activities and could be used in the development of pharmaceutical formulation as an alternative to conventional mastitis therapy.
Highlights
The economic rise of the dairy market all over the world with the importance of delivering healthy and safety dairy products highlights the importance of managing milk production in a secure and sustainable manner [1,2,3]
The most common among the pathogens was E. coli, which was identified in six samples (19.35%), followed by five (16.13%) samples with Streptococcus spp., while Staphylococcus spp. coagulase negative, Streptococcus uberis, Streptococcus dysgalactiae, Klebsiella oxytoca, and Enterobacter sakazakii were found in one sample each (3.23%) (Figure 1)
The essential oils (EOs) tested in our study showed notable antioxidant potential, similar to the results of other authors [20,21,27,28,32,45], the general comparison of the results obtained in different labs is sometimes difficult because of different experimental conditions and presentation of the results, different methods of antioxidant potential evaluation, and so on
Summary
The economic rise of the dairy market all over the world with the importance of delivering healthy and safety dairy products highlights the importance of managing milk production in a secure and sustainable manner [1,2,3]. In Serbia, milk production is organized in two different systems; small household farms with ten to twenty animals and large farms counting several hundred to several thousand cows [4]. The etiology of mastitis is complex, and both mechanical and chemical factors that can be attributed to omissions in the way of housing and the procedure of milking cows certainly could contribute to the development of this disease [8]. This problem is more represented on large farms where little human labor is employed. While intramammary administration implies application of antibiotics directly in mammary gland through teat channel in order to achieve their effect locally in the gland, parenteral administration is application where the digestive tract is bypassed (e.g., intramuscularly, subcutaneously, intravenously) in order to achieve systemic effect including mammary gland tissue
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