Essential Oils: Partnering with Antibiotics

Essential oils (EO) are volatile, non-lipid-based oils produced as a plant defense mechanism. Studies from our group have validated the potential usefulness of EOs to synergistically and additively work with antibiotics. In this book chapter, we aim to outline some background on the EOs and their uses and applications, to discuss the different mechanisms of action in partnering with antibiotics, and, finally, to explore their potential use against multidrug-resistant bacteria. Applications of EO in therapy will enable the revival of previously sidelined antibiotics and enhance the development of new drug regimens to better mitigate what may be the biggest health challenge by year 2050

Innovations in MDR therapy: essential oil applications

There are three common outcomes when testing the application of combinatory therapies for potential use in the clinical setting against multi-drug resistant (MDR) bacteria; whether synergistic, additive or antagonistic. Due to their relatively more favourable outcomes, antibiotics and adjuvant achieving synergism have been the primary focus in the development of therapeutics thus far; this has also resulted in less attention given to additive interactions, which may be equally effective. Hence, in this study, the authors investigated the effects of additivity using a representative combination model involving Cinnamomum verum (cinnamon bark) essential oil (CBO) and meropenem, a carbapenem class of antibiotics. Based on the zeta potential measurements, outer membrane permeability and scanning electron microscopy, synergistic and additive interactions of cinnamon bark oil (CBO) indicated comparable bacterial membrane disruption, alluding similar degrees of cell perturbations at the molecular level. Results from this study suggests that further investigations should be looked into for combinatorial therapeutic pairs achieving additive indices so as not to disqualify potentially useful alternatives in antibiotic therapy

Lavender essential oil induces oxidative stress which modifies teh bacterial membrane permeability of carbapenase producing Klebsiella pnuemoniae

Misuse of antibiotics in the clinical and agricultural sectors has caused the emergence of multidrugresistant (MDR) Klebsiella pneumoniae which contributes a threat to human health. In this study, we assessed the feasibility of lavender essential oil (LVO) as an antimicrobial agent in combinatory therapy with meropenem in suppressing the growth of carbapenemase-producing K. pneumoniae (KPC-KP). Synergistic interactions between LVO and meropenem were detected, which signifcantly reduce the inhibitory concentration of both LVO and meropenem by 15 and 4-fold respectively. Comparative proteomic profling identifed a disruption in the bacterial membrane via oxidative stress that was indicated by loss of membrane and cytoplasmic proteins and the upregulation of oxidative regulators. As a proof of concept, zeta potential measurements showed a change in cell surface charge while outer membrane permeability measurement indicated an increase in membrane permeability following exposure to LVO. This was indicative of a disrupted outer membrane. Ethidium bromide infux/efux assays demonstrated no signifcant efux pump inhibition by LVO, and scanning electron microscopy revealed irregularities on the cell surface after exposure to LVO. Oxidative stress was also detected with increased level of ROS and lipid peroxidation in LVO-treated cells. In conclusion, our data suggest that LVO induced oxidative stress in K. pneumoniae which oxidizes the outer membrane, enabling the infux of generated ROS, LVO and meropenem into the bacterial cells, causing damage to the cells and eventually death