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

Th is research examined the antimicrobial eff ect of Lavandula stoechas (lavender) and Origanum majorana (marjoram) essential oil against three pathogens: Staphylococcus aureus, Streptococcus agalactiae, and Escherichia coli. Gas chromatography- mass spectrometry (GC/MS) analysis revealed that the main components of the lavender and marjoram oils were 17-Pentatriacontene, Linalyl acetate, Eucalyptol, linalool and 3-Cyclohexene-1-ol,4-methyl-1-(1-methylethyl)-,(R)-, α-terpineol, P-cymene, 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, time-kill 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. Th e MIC and MBC of the marjoram ranged from 0.62 - 1.87% v/v and 1.25 - 3.75% v/v, respectively. Th e MIC ranged from 2.5 - 5% v/v and MBC between 5 - 10% v/v for lavender + marjoram combination. In time-kill assays, the presence of lavender and marjoram oils at a sub-MIC concentration signifi cantly reduced the bacterial population in 4, 10 and 24 h. Generally, essential oil of marjoram had greater antibacterial activity than lavender against all mastitis-causing pathogens tested and has the potential to be evaluated as an alternative or adjunct to antibiotics in the treatment of bovine mastitis.