Antibacterial activity of lavender essential oil and linalool combined with gentamicin on selected bacterial strains

The aim of this study was to verify the existence of the synergistic antibacterial effect of lavender essential oil and linalool individually combined with the antibacterial drug gentamicin. We investigated in vitro the effectiveness of the combinations of gentamicin and lavender essential oil and of gentamicin and linalool against the following strains: Staphylococus aureus ATCC 25923, Staphylococus aureus MRSA and Pseudomonas aeruginosa ATCC 9027. In order to determine the sensitivity of these microorganisms, we determined the minimum inhibitory concentration (MIC - Minimal Inhibitory Concentration). The study of the interaction of gentamicin with lavender oil and linalool was evaluated by the checkerboard method. Synergistic interaction between lavender essential oil and gentamicin and between linalool and gentamicin was observed against Staphylococcus aureus ATCC 25923 and Staphylococcus aureus MRSA. In particular, a very strong synergistic interaction was observed against Staphyloccocus aureus MRSA (lavender essential oil FIC index = 0.14; linalool FIC index = 0.13). In contrast, combinations of gentamicin and lavender essential oil and of gentamicin and linalool were less effective against Pseudomonas aeruginosa growth.