Abstract
Mannosylerythritol lipid-B (MEL-B), which comprises ester-bonded hydrophilic ME and hydrophobic fatty acids, is a bio-surfactant with various unique properties, including antimicrobial activity against most gram-positive bacteria. The gram-positive Staphylococcus aureus is a causative pathogen of dairy cattle mastitis, which results in considerable economic loss in the dairy industry. Here, we demonstrate the efficacy of MEL-B as a disinfectant against bovine-derived S. aureus and elucidate a mechanism of action of MEL-B in the inhibition of bacterial growth. The growth of bovine mastitis causative S. aureus BM1006 was inhibited when cultured with MEL-B above 10 ppm. The activity of MEL-B required fatty acids (i.e., caprylic and myristoleic acids) as ME, the component of MEL-B lacking fatty acids, did not inhibit the growth of S. aureus even at high concentrations. Importantly, ME-bound fatty acids effectively inhibited the growth of S. aureus when compared with free fatty acids. Specifically, the concentrations of ME-bound fatty acids and free caprylic and myristoleic acids required to inhibit the growth of S. aureus were 10, 1442, and 226 ppm, respectively. The involvement of ME in the antimicrobial activity of MEL-B was confirmed by digestion of MEL-B with alkali, which dissociated ME and fatty acids. These results indicated that a mechanism of action of MEL-B in inhibiting the growth of S. aureus could be explained by the effective transporting of antimicrobial fatty acids to the bacterial surface via hydrophilic ME.
Highlights
In the livestock industry, large amounts of antibiotics have been extensively used to cure domestic animals suffering from infectious diseases such as mastitis, diarrhea, and pneumonia (Berendsen et al 2015; Kromker and Leimbach 2017)
Our study aimed to evaluate Mannosylerythritol lipid-B (MEL-B) as a possible disinfectant for use in the livestock industry to control the spread of S. aureus strains, including methicillin-resistant S. aureus (MRSA)
We demonstrated that the growth of S. aureus BM1006, which belongs to the
Summary
Large amounts of antibiotics have been extensively used to cure domestic animals suffering from infectious diseases such as mastitis, diarrhea, and pneumonia (Berendsen et al 2015; Kromker and Leimbach 2017). International Education and Research Center for Food and Agricultural Immunology, Graduate School of Agricultural Science, Tohoku University, 468‐1 Aoba, Aramaki, Aoba‐ku, Sendai, Miyagi 980‐8572, Japan. Laboratory of Functional Morphology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 980‐8572, Japan. Division of Bacterial and Parasitic Disease, National Institute of Animal Health, Bacterial Pathogenesis Research Unit, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305‐0856, Japan. Laboratory of Animal Microbiology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 980‐8572, Japan. Laboratory of Animal Health Science, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 980‐8572, Japan. Division of Mucosal Vaccines, International Research and Development Center for Mucosal Vaccines, The Institute of Medical Science, The University of Tokyo, Tokyo 108‐8639, Japan Page 2 of 10. Considering that contagious bacteria can spread globally, the idea of “One Health” that pursues the health of animals, humans, and the environment without the use of excess antibiotics has been widely accepted (Collignon 2015; McEwen and Collignon 2018)
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