title: Deletion of liaR Reverses Daptomycin Resistance in Enterococcus faecium Independent of the Genetic Background.
abstract: We have shown previously that changes in LiaFSR, a three-component regulatory system predicted to orchestrate the cell membrane stress response, are important mediators of daptomycin (DAP) resistance in enterococci. Indeed, deletion of the gene encoding the response regulator LiaR in a clinical strain of Enterococcus faecalis reversed DAP resistance (DAP-R) and produced a strain hypersusceptible to antimicrobial peptides. Since LiaFSR is conserved in Enterococcus faecium, we investigated the role of LiaR in a variety of clinical E. faecium strains representing the most common DAP-R genetic backgrounds. Deletion of liaR in DAP-R E. faecium R446F (DAP MIC of 16 μg/ml) and R497F (MIC of 24 μg/ml; harboring changes in LiaRS) strains fully reversed resistance (DAP MICs decreasing to 0.25 and 0.094 μg/ml, respectively). Moreover, DAP at concentrations of 13 μg/ml (achieved with human doses of 12 mg/kg body weight) retained bactericidal activity against the mutants. Furthermore, the liaR deletion derivatives of these two DAP-R strains exhibited increased binding of boron-dipyrromethene difluoride (BODIPY)-daptomycin, suggesting that high-level DAP-R mediated by LiaR in E. faecium involves repulsion of the calcium-DAP complex from the cell surface. In DAP-tolerant strains HOU503F and HOU515F (DAP MICs within the susceptible range but bacteria not killed by DAP concentrations of 5× the MIC), deletion of liaR not only markedly decreased the DAP MICs (0.064 and 0.047 μg/ml, respectively) but also restored the bactericidal activity of DAP at concentrations as low as 4 μg/ml (achieved with human doses of 4 mg/kg). Our results suggest that LiaR plays a relevant role in the enterococcal cell membrane adaptive response to antimicrobial peptides independent of the genetic background and emerges as an attractive target to restore the activity of DAP against multidrug-resistant strains.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA Molecular Genetics and Antimicrobial Resistance Unit, Universidad El Bosque, Bogota, Colombia.
authors.forename: Diana
authors.initials: D
authors.lastname: Panesso
authors.affiliation: Molecular Genetics and Antimicrobial Resistance Unit, Universidad El Bosque, Bogota, Colombia.
authors.forename: Jinnethe
authors.initials: J
authors.lastname: Reyes
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA.
authors.forename: Elizabeth P
authors.initials: EP
authors.lastname: Gaston
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA.
authors.forename: Morgan
authors.initials: M
authors.lastname: Deal
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Londoño
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nigo
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA Clínica Alemana de Santiago and Universidad del Desarrollo, Santiago, Chile.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Munita
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA.
authors.forename: William R
authors.initials: WR
authors.lastname: Miller
authors.affiliation: Department of BioSciences, Rice University, Houston, Texas, USA.
authors.forename: Yousif
authors.initials: Y
authors.lastname: Shamoo
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA University of Houston College of Pharmacy, Houston, Texas, USA.
authors.forename: Truc T
authors.initials: TT
authors.lastname: Tran
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA Molecular Genetics and Antimicrobial Resistance Unit, Universidad El Bosque, Bogota, Colombia Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, Texas, USA cesar.arias@uth.tmc.edu.
authors.forename: Cesar A
authors.initials: CA
authors.lastname: Arias
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D001896:Boron Compounds / Q000737:chemistry / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017576:Daptomycin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000187:drug effects / Q000235:genetics*; D016984:Enterococcus faecium / Q000187:drug effects* / Q000235:genetics*; D017353:Gene Deletion; D000068617:Genetic Background; D008826:Microbial Sensitivity Tests
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001896:Boron Compounds; D017576:Daptomycin