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Antimicrobial Agents and Chemotherapy, December 2001, p. 3574-3579, Vol. 45, No. 12
0066-4804/01/$04.00+0   DOI: 10.1128/AAC.45.12.3574-3579.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Characterization of emeA, a norA Homolog and Multidrug Resistance Efflux Pump, in Enterococcus faecalis

Brandie M. Jonas,1,2 Barbara E. Murray,1,2,3 and George M. Weinstock1,3,*

Department of Microbiology and Molecular Genetics,1 Center for the Study of Emerging and Re-emerging Pathogens,3 and Division of Infectious Diseases,2 University of Texas Medical School, Houston, Texas 77030

Received 28 February 2001/Returned for modification 9 July 2001/Accepted 7 September 2001

We hypothesized that multidrug resistance efflux pumps (MDRs) may be contributing to the drug resistance of enterococci. We recently identified potential MDR-encoding genes in the Enterococcus faecalis V583 genome. Among the putative MDRs, we found a gene that encodes a NorA homolog and have characterized this enterococcal MDR in the present study. A mutant from which the enterococcal NorA homolog has been deleted has reduced resistance to several NorA substrates. Complementation of the deletion mutant with the wild-type gene verified the involvement of this enterococcal gene in resistance to ethidium bromide (EtBr) and norfloxacin. Known MDR inhibitors (reserpine, lansoprazole, and verapamil) inhibit the efflux of EtBr and norfloxacin in wild-type strain OG1RF. A fluorescence assay with EtBr allowed us to quantitate the efflux capability of the enterococcal NorA pump. On the basis of these results, we have named this enterococcal gene emeA (enterococcal multidrug resistance efflux).

* Corresponding author. Mailing address: Human Genome Sequencing Center, Baylor College of Medicine, One Baylor Plaza, Alkek N1519, Houston, TX 77030. Phone: (713) 798-6539. Fax: (713) 798-5741. E-mail: gwstock{at}bcm.tmc.edu.

Antimicrobial Agents and Chemotherapy, December 2001, p. 3574-3579, Vol. 45, No. 12
0066-4804/01/$04.00+0   DOI: 10.1128/AAC.45.12.3574-3579.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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