Multidrug resistance and major facilitator superfamily antimicrobial efflux pumps of the ESKAPEE pathogen Staphylococcus aureus

Abstract

Multiple drug-resistant Staphylococcus aureus bacterial pathogens are causative agents of serious infectious disease and are responsible for significant morbidity and mortality rates. Of particular concern in the public health domain are strains of methicillin-resistant S. aureus (MRSA), a member of the Enterococcus faecium, S. aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp., Escherichia coli (ESKAPEE) group of bacterial pathogens, many of which are recalcitrant to effective chemotherapy in the clinical setting due to their resistance to multiple antimicrobial agents. An important mechanism that confers multi-drug resistance in MRSA involves the active efflux of structurally different antimicrobial agents by members of the major facilitator superfamily (MFS) of proteins. The multidrug efflux pumps of the MFS share similar amino acid sequences, protein structures, and a common evolutionary origin. As such, the multidrug efflux pumps of the MFS are thought to operate by a similar solute transport mechanism and, thus, represent suitable targets for modulating their transport activities. This review article addresses MRSA as a serious pathogen, the mechanisms of antimicrobial resistance, and the functional and structural roles of the multidrug efflux pumps of the MFS in conferring pathogenicity.