Antibacterial eff ect of Lavandula stoechas and Origanum majorana essential oils against Staphylococcus aureus, Streptococcus agalactiae, and Escherichia coli

This research examined the antimicrobial effect of Lavandula stoechas (lavender) and Origanum majorana (marjoram) essential oil against three mastitiscausing pathogens: Staphylococcus aureus, Streptococcus agalactiae, and Escherichia coli. Gas chromatographymass spectrometry (GC/MS) analysis revealed that the main components of the lavender and marjoram oils were 17Pentatriacontene, Linalyl acetate, Eucalyptol, linalool and 3Cyclohexene1ol,4methyl1(1methylethyl),(R), αterpineol, Pcymene, respectively. Broth dilution testing was performed using autoclaved whole milk instead of broth to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of essential oils alone and in combination. In addition, timekill assay of lavender and marjoram oils were determined in milk up to 24 h. MIC values ranged from 3.12 4.37% v/v and MBC between 6.25 8.75% v/v for the lavender. The MIC and MBC of the marjoram ranged from 0.62 1.87% v/v and 1.25 3.75% v/v, respectively. The MIC ranged from 2.5 5% v/v and MBC between 5 10% v/v for lavender + marjoram combination. In timekill assays, the presence of lavender and marjoram oils at a subMIC concentration significantly reduced the bacterial population in 4, 10 and 24 h. Generally, essential oil of marjoram had greater antibacterial activity than lavender against all mastitiscausing pathogens tested and has the potential to be evaluated as an alternative or adjunct to antibiotics in the treatment of bovine mastitis.