Microbiology news and views
J. Mol. Micro. Biotechnol. 3: 255-264
Multidrug Efflux Pumps and Antimicrobial Resistance in
Pseudomonas aeruginosa and Related Organisms
Keith Poole
Pseudomonas aeruginosa is an opportunistic human pathogen characterized by an innate resistance to
multiple antimicrobial agents. A major contribution to this intrinsic multidrug resistance is provided by a number
of broadly-specific multidrug efflux systems, including MexAB-OprM and MexXY-OprM. In addition, these and
two additional tripartite efflux systems, MexCD-OprJ and MexEF-OprN, promote acquired multidrug resistance as
a result of mutational hyperexpression of the efflux genes. In addition to antibiotics, these pumps promote
export of numerous dyes, detergents, inhibitors, disinfectants, organic solvents and homoserine lactones involved
in quorum sensing. The efflux pump proteins are highly homologous and consist of a cytoplasmic
membrane-associated drug-proton antiporter of the Resistance-Nodulation-Division (RND) family, an outer
membrane channel-forming protein [sometimes called outer membrane factor (OMF)] and a periplasmic membrane
fusion protein (MFP). Homologues of these systems have been described in
Stenotrophomonas maltophilia, Burkholderia
cepacia, Burkholderia pseudomallei and the non-pathogen
Pseudomonas putida, where they play a role in export of and resistance to multiple antimicrobial agents and/or organic solvents. Although the
natural function of these multidrug efflux systems is largely unknown, their contribution to antibiotic resistance
and their conservation in a number of important human pathogens makes them logical targets for
therapeutic intervention.
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