Hovorková P., Laloučková K., Skřivanová E. (2018): Determination of in vitro antibacterial activity of plant oils containing medium-chain fatty acids against Gram-positive pathogenic and gut commensal bacteria. Czech J. Anim. Sci., 63, 119-125.Increasing antibiotic resistance has led to a ban on antibiotic use in feed additives in the EU. Therefore, new non-antibiotic, pathogen-inhibiting agents are urgently needed. Inhibitory effects of eight plant oils containing medium-chain fatty acids (MCFAs) were evaluated against Gram-positive pathogenic and beneficial bacteria. The oils tested were palm, red palm, palm kernel (Elaeis guineensis), coconut (Cocos nucifera), babassu (Attalea speciosa), murumuru (Astrocaryum murumuru), tucuma (Astrocaryum vulgare), and Cuphea oil (Cuphea ignea); the method used was broth microdilution, and the findings were expressed as minimum inhibitory concentration (80%). Both hydrolyzed and unhydrolyzed forms of the oils were tested. MCFA hydrolysis was catalyzed by porcine pancreas lipase. The selective effect of the hydrolyzed forms of tested oils was highly evident. While the hydrolyzed oils were active against all tested bacteria (Clostridium perfringens, Enterococcus cecorum, Listeria monocytogenes, and Staphylococcus aureus), at 0.14-4.5 mg/ml, the same oils did not show any effect on commensal bacteria (Bifidobacterium spp. and Lactobacillus spp.). Tucuma and Cuphea seed oils showed the strongest antibacterial activity. Unhydrolyzed forms of all tested oils exerted no antibacterial effect against any test bacteria. This study, thus, forms a basis for the development of selective inhibitors in animal husbandry.
Due to its large surface area, the skin is susceptible to various injuries, possibly accompanied by the entrance of infective agents into the body. Commensal organisms that constitute the skin microbiota play important roles in the orchestration of cutaneous homeostasis and immune competence. The opportunistic pathogen Staphylococcus aureus is present as part of the normal biota of the skin and mucous membranes in both humans and animals, but can cause disease when it invades the body either due to trauma or because of the impaired immune response of the host. Colonization of livestock skin by S. aureus is a precursor for majority of bacterial skin infections, which range from boils to sepsis, with the best-characterized being bovine mastitis. Antibiotic treatment of these infections can contribute to the promotion of resistant bacterial strains and even to multidrug resistance. The development of antibiotic resistance to currently available antibiotics is a worldwide problem. Considering the increasing ability of bacteria to effectively resist antibacterial agents, it is important to reduce the livestock consumption of antibiotics to preserve antibiotic effectiveness in the future. Plants are recognized as sources of various bioactive substances, including antibacterial activity towards clinically important microorganisms. This review provides an overview of the current knowledge on the major groups of phytochemicals with antibacterial activity and their modes of action. It also provides a list of currently known and used plant species aimed at treating or preventing bacterial skin infections in livestock.
Infections caused by Staphylococcus aureus are a serious global threat, and with the emergence of antibiotic resistance, even more difficult to treat. One of the possible complications in antistaphylococcal therapy represents negative interactions of antibiotics with food. In this study, the in vitro interaction between oxacillin and crude palm seed oil from Astrocaryum vulgare, Cocos nucifera, and Elaeis guineensis against nine strains of S. aureus was determined using the checkerboard method. Lauric acid was identified as a major constituent of all tested oils by gas chromatography. The results showed strong concentration dependent antagonistic interactions between palm oils and oxacillin with values of fractional inhibitory concentrations indices ranging from 4.02 to 8.56 at concentrations equal or higher than 1024 µg/mL of the tested oils. Similarly, lauric acid in combination with oxacillin produced antagonistic action with fractional inhibitory concentration indices ranging from 4.01 to 4.28 at 1024 µg/mL. These findings suggest that interference between oxacillin and palm oils and their constituents can negatively affect the treatment of staphylococcal infections in humans and other animals.
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