Antimicrobial resistance represents a significant challenge to future healthcare
provision.An acronym ESKAPEE has been derived from the names of the organisms recognised
as the major threats although there are a number of other organisms, notably Neisseria
gonorrhoeae, that have become equally challenging to treat in the clinic. These pathogens
are characterised by the ability to rapidly develop and/or acquire resistance mechanisms in
response to exposure to different antimicrobial agents. A key part of the armoury of these pathogens is a series
of efflux pumps, which effectively exclude or reduce the intracellular concentration of a large number of
antibiotics, making the pathogens significantly more resistant. These efflux pumps are the topic of considerable
interest, both from the perspective of basic understanding of efflux pump function, and its role in drug
resistance but also as targets for the development of novel adjunct therapies. The necessity to overcome antimicrobial
resistance has encouraged investigations into the characterisation of resistance-modifying efflux
pump inhibitors to block the mechanisms of drug extrusion, thereby restoring antibacterial susceptibility and
returning existing antibiotics into the clinic. A greater understanding of drug recognition and transport by
multidrug efflux pumps is needed to develop clinically useful inhibitors, given the breadth of molecules that
can be effluxed by these systems. This review discusses different bacterial EPIs originating from both natural
source and chemical synthesis and examines the challenges to designing successful EPIs that can be useful
against multidrug resistant bacteria.