title: Citrus-derived oil inhibits Staphylococcus aureus growth and alters its interactions with bovine mammary cells.
abstract: This experiment examined the effects of cold-pressed, terpeneless citrus-derived oil (CDO) on growth of Staphylococcus aureus, which a major cause of contagious bovine mastitis, and invasion of bovine mammary cells (MAC-T). To determine minimum inhibitory concentration, we used the broth dilution method, using CDO concentrations range from 0.0125 to 0.4% with 2-fold dilutions. Growth inhibition was examined by adding 0.00, 0.05, 0.025, 0.0125, and 0.00625% CDO to 10(5) cfu/mL S. aureus in nutrient broth and enumerating colonies after serial dilution. In a 96-well plate, S. aureus (10(7) cfu/mL) was allowed to form a biofilm, treated with 0, 0.025, 0.5, or 1% CDO, and then was measured using a spectrophotometer. Cytotoxic effect on immortalized MAC-T cells was also examined at various concentrations of CDO using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. We observed that the minimum inhibitory concentration of CDO to inhibit the growth of S. aureus in vitro was 0.025% CDO. A time kill curve for CDO action on S. aureus over 4h was generated. The CDO completely eliminated S. aureus after 3h of incubation at a concentration of 0.25%, or after 2h of incubation at concentrations of 0.05%. It was also observed that CDO had no effect on preformed biofilms except at a concentration of 0.05%, in which a significant reduction in the measured absorbance was noted. In addition, the association and invasion of S. aureus to MAC-T cells were significantly inhibited after 1h of treatment with CDO. Citrus-derived oil was also able to increase cellular proliferation of MAC-T cells at concentrations up 0.05% and had no effect at a concentration of 0.1% after 1 h. Our data suggests that CDO should be considered for further research as a preventive and therapeutic against bovine mastitis.
authors.affiliation: Department of Animal and Avian Sciences, University of Maryland, College Park 20742.
authors.forename: C
authors.initials: C
authors.lastname: Federman
authors.affiliation: Department of Animal and Avian Sciences, University of Maryland, College Park 20742.
authors.forename: J
authors.initials: J
authors.lastname: Joo
authors.affiliation: Department of Animal and Avian Sciences, University of Maryland, College Park 20742.
authors.forename: J A
authors.initials: JA
authors.lastname: Almario
authors.affiliation: Department of Animal and Avian Sciences, University of Maryland, College Park 20742.
authors.forename: S
authors.initials: S
authors.lastname: Salaheen
authors.affiliation: Department of Animal and Avian Sciences, University of Maryland, College Park 20742; Center for Food Safety and Security Systems, University of Maryland, College Park 20742. Electronic address: dbiswas@umd.edu.
authors.forename: D
authors.initials: D
authors.lastname: Biswas
mesh_terms: D000818:Animals; D002417:Cattle; D002957:Citrus; D005260:Female; D008414:Mastitis, Bovine; D013203:Staphylococcal Infections; D013211:Staphylococcus aureus / Q000187:drug effects*
keywords: Staphylococcus aureus; antibiofilm; citrus oil; inhibition; mastitis