Antimicrobial Action of Oleanolic Acid on Listeria monocytogenes, Enterococcus faecium, and Enterococcus faecalis

Abstract

This study investigated the antimicrobial action of oleanolic acid against Listeria monocytogenes, Enterococcus faecium, and Enterococcus faecalis. To determine the cytotoxicity of oleanolic acid, HEp-2 cells were incubated with oleanolic acid at 37oC. MICs (minimal inhibition concentrations) for L. monocytogenes, E. faecium, and E. faecalis were determined using two-fold microdilutions of oleanolic acid, and bacterial cell viability was then assessed by exposing the bacteria to oleanolic acid at 2 × MIC. To investigate the mode of antimicrobial action of oleanolic acid, we measured leakage of compounds absorbing at 280 nm, along with propidium iodide uptake. Scanning electron microscope (SEM) images were also analysed. The viability of HEp-2 cells decreased (P < 0.05) at oleanolic acid concentrations greater than 128 μg mL-1. The MICs were 16-32 μg mL-1 for L. monocytogenes and 32-64 μg mL-1 for E. faecium and E. faecalis, and bacterial cell viability decreased (P < 0.05) about 3-4 log CFU mL-1 after exposure to 2 × MIC of oleanolic acid. Leakage of 280 nm absorbing materials and propidium iodide uptake was higher in oleanolic acid –treated cells than in the control. The cell membrane was damaged in oleanolic acid-treated cells, but the control group had intact cell membrane in SEM images. The results indicate that oleanolic acid can kill L. monocytogenes, E. faecium, and E. faecalis by destroying the bacterial cell membrane.

Synergy between Ursolic and Oleanolic Acids from Vitellaria paradoxa Leaf Extract and β-Lactams against Methicillin-Resistant Staphylococcus aureus: In Vitro and In Vivo Activity and Underlying Mechanisms

“…Until now, few studies have investigated the mechanism by which UA and OA exert their antibacterial effects, often suggesting that they target the bacterial membrane or the peptidoglycan [ 21 , 23 ]. Due to their lipophilic character, UA and OA can accumulate in biological membranes, resulting in swelling and increased fluidity, as demonstrated using liposomes reconstituted from bacterial lipids [ 24 ].…”

“…MRSA BCBPM073 carrying a gfp-pbp2 fusion was grown in TSB and incubated during 30 min without (DMSO) or with 1× MIC of Oxacillin (Oxa), UA or OA and observed by conventional (lower panel) and superresolution structured illumination (upper panel) microscopy. The localization of PBP2 was determined by calculating the fluorescence ratio (FR) ( a – c )/( b , c ) where “ a ” corresponds to the fluorescence found at the septum, “ b ” to the fluorescence of the peripheral membrane and “ c ” to the background fluorescence [ 23 ], as illustrated in the lower part of the figure. Values are the means ± SD from measurements of fluorescence ratios of 200 cells in each sample.…”

Oleanolic Acid and Its Derivatives: Biological Activities and Therapeutic Potential in Chronic Diseases

“…Moreover, pathogens have emerged as notable factors, not just in the complications, but also in the progression of chronic diseases [ 73 ]. For example, OA exhibited antimicrobial action against Listeria monocytogenes , Enterococcus faecalis and Enterococcus faecium by damaging their cell membranes [ 74 ]. To further characterize the function of OA in other microorganisms that causes various ailments, a number of oleanane triterpenoids compounds including oleanolic acid and epi-oleanolic acid were isolated singly from the pericarp of a medicinal food plant, Akebia trifoliate [ 75 ].…”

Antibiofilm and Membrane-Damaging Potential of Cuprous Oxide Nanoparticles against Staphylococcus aureus with Reduced Susceptibility to Vancomycin

“…This rapid increase in PI uptake confirms that the antibiofilm activity of Cu 2 O-NPs was due to cell membrane disruption. Because of its large size and negative charge, PI cannot pass through the intact membranes of bacteria (38).…”