Multi drug resistance efflux pumps (MDRs) contribute to the intrinsic drug resistance of many organisms. Although the primary function of most of these proteins is unknown, it is clear that these proteins are capable of extruding a wide spectrum of unrelated compounds out of cells. Because of the growing concern over emerging multi drug resistant strains of enterococci, we hypothesized that MDRs may be partly responsible for this growing problem. Using a genomics approach, we identified potential MDRs in the Enterococcus faecalis: V583 genome. As a test case, we chose to characterize the enterococcal NorA homolog. A NorA mutant was constructed in E. faecalis OG1RF and tested for reduced resistance to several NorA substrates. Complementation of Delta-norA with the wild type gene was performed to verify involvement of the enterococcal gene in drug resistance. Known MDR inhibitors were also analyzed for their ability to inhibit drug efflux in enterococci. A fluorescence assay using ethidium bromide (EtBr) allowed us to visualize the efflux capability of the enterococcal NorA protein.
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Identification of Multi Drug Resistance Efflux Pumps (MDRs) in Enterococcus faecalis: Characterization of an MDR NorA Homolog