The mechanism of antibacterial action of Essential Oils against Enterococcus faecium: the role of transport channels




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Peer reviewed


Aims The overall aim of this study is to establish the mechanisms of action of a novel formulation of plant extracts known to be effective against Vancomycin Resistant E. faecium (VRE) isolates. Channels in the bacterial cell wall were assessed to see if they act in a similar way to mammalian cell Transient Receptor Potential Channels (TRPV1) that are known to be activated by the EOs and capsaicin. Methods and results Growth curves and viable counts were conducted for E. faecium (VSE) in the presence of the TRPV1 channel blocker AMG517, EO blend (carvacrol 0.2µl and cuminaldehyde 25µl) and capsaicin. Microarray data was used to assess which genes associated with ion channels were differentially regulated in the presence of EO blend. AMG517 (10nM to 90nM) did not limit the inhibitory effect of capsaicin (Minimum Inhibitory Concentration:1.6mM) or the EO blend on E. faecium. This suggests that a homologue of TRPV1 does not exist in E. faecium. Microarray data showed that there are genes encoding channels including kup, bcr, gsia_1, mscL, gla_2, ylob that were differentially regulated when exposed to the EO blend. Conclusions The microarray data suggests that cell wall channels are involved in the mechanism of action of EOs; despite the antimicrobial action of capsaicin on E. faecium results are not consistent with the involvement of TRPV1 homologue in bacteria.
Significance of study Due to an increase in antibiotic resistance, novel antimicrobial compounds with mechanisms of action that are effective against multi-drug resistant (MDR) microorganisms are of particular interest1,2. Although a homologue of TRPV1 was not identified, microarray data demonstrates that the EO blend is having an effect on genes involved in transport mechanisms. Further investigations are required to ascertain the exact mechanism of action of EOs against bacteria in order for them to be exploited as novel antimicrobials.


  1. Wikaningtyas P, Sukandar EY. The antibacterial activity of selected plants towards resistant bacteria isolated from clinical specimens. Asian Pac J Trop Biomed. 2016;6(1):16-19. doi:10.1016/j.apjtb.2015.08.003
  2. Simpkin VL, Renwick MJ, Kelly R, Mossialos E. Incentivising innovation in antibiotic drug discovery and development: Progress, challenges and next steps. J Antibiot (Tokyo). 2017;70(12):1087-1096. doi:10.1038/ja.2017.124




Alhareth, Z., Owen, L., Dixon, J., McKechine, K., Smith, S. and Laird, K. (2018) The mechanism of antibacterial action of Essential Oils against Enterococcus faecium: the role of transport channels [poster]. Society for Applied Microbiology Antimicrobial Resistance Meeting 2018, London, November 2018.


Research Institute

Leicester Institute for Pharmaceutical Innovation - From Molecules to Practice (LIPI)