Mode of Action: Synergistic Interaction of Peppermint (Mentha x piperita L. Carl) Essential Oil and Meropenem Against Plasmid-Mediated Resistant E. coli

This study investigated the bactericidal mechanism of peppermint essential oil (PEO) when used singly and in combination with meropenem against multidrug resistant Escherichia coli. Chemical compositions of PEO were identified via GC-MS, followed by time-kill analysis which was performed to evaluate the antibacterial activities of PEO and meropenem. Furthermore, outer membrane permeability test, zeta potential measurement and scanning electron microscopy were performed to evaluate the ability of PEO in bacterial membrane disruption. Next, anti-quorum sensing assay was performed to assess the ability of PEO in quorum sensing inhibition. A complete killing activity was observed within five minutes of treatment with PEO and meropenem at sub-lethal concentrations. In addition, the outer membrane permeability test and zeta potential measurement performed indicated increase in the membrane permeability and membrane disruption which can be observed in the scanning electron micrograph. Furthermore, significant decrease in the light production of E. coli pSB1075 treated by PEO indicates the presence of quorum sensing inhibitors within PEO. The findings suggest that PEO has the ability to disrupt the bacterial outer membrane which increases membrane permeability, in addition to the possible inhibition of bacterial quorum sensing ability in multidrug resistant E. coli, aiding in the reversal of antibiotic resistance.