Antimicrobial Drug Efflux Pumps in Staphylococcus aureus

Abstract

The highly adaptive opportunistic human pathogen, Staphylococcus aureus, contains a large number of integral membrane transport proteins important in homeostasis and pathogenesis. Included in this group are multidrug efflux pumps which play a role in antimicrobial resistance by reducing the intracellular concentration of drug compounds through active extrusion from the cell. S. aureus encodes many such drug efflux proteins, which fall into four out of the six currently recognized drug transporter families. These efflux pumps can confer host resistance against a vast number of clinically relevant antimicrobials, including macrolides, quinolones, streptogramins, and tetracyclines, as well as biocides such as biguanidines, diamidines, and quaternary ammonium compounds. The prevalence of these drug efflux determinants, either chromosomally or plasmid encoded, has been established worldwide, with clinical isolates expressing numerous multidrug transport proteins being continually identified. In addition to the characterized drug transporters, the recent surge in sequencing has also revealed a number of putative drug efflux proteins; some of these may share characteristics of known pumps, but, as seen with the recent addition of the proteobacterial antimicrobial compound efflux family, may represent proteins which are unique.