Deletion of liaR Reverses Daptomycin Resistance in Enterococcus faecium Independent of the Genetic Background
Journal
Antimicrobial Agents and Chemotherapy
ISSN
0066-4804
1098-6596
Date Issued
2015
Author(s)
Diana Panesso
Jinnethe Reyes
Elizabeth P. Gaston
Morgan Deal
Alejandra Londoño
Masayuki Nigo
William R. Miller
Yousif Shamoo
Truc T. Tran
Cesar A. Arias
Type
Resource Types::text::journal::journal article
URL Institutional Repository
Abstract
<jats:title>ABSTRACT</jats:title>
<jats:p>
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
<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Enterococcus faecalis</jats:named-content>
reversed DAP resistance (DAP-R) and produced a strain hypersusceptible to antimicrobial peptides. Since LiaFSR is conserved in
<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Enterococcus faecium</jats:named-content>
, we investigated the role of LiaR in a variety of clinical
<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">E. faecium</jats:named-content>
strains representing the most common DAP-R genetic backgrounds. Deletion of
<jats:italic>liaR</jats:italic>
in DAP-R
<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">E. faecium</jats:named-content>
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
<jats:italic>liaR</jats:italic>
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
<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">E. faecium</jats:named-content>
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
<jats:italic>liaR</jats:italic>
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.
</jats:p>
<jats:p>
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
<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Enterococcus faecalis</jats:named-content>
reversed DAP resistance (DAP-R) and produced a strain hypersusceptible to antimicrobial peptides. Since LiaFSR is conserved in
<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Enterococcus faecium</jats:named-content>
, we investigated the role of LiaR in a variety of clinical
<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">E. faecium</jats:named-content>
strains representing the most common DAP-R genetic backgrounds. Deletion of
<jats:italic>liaR</jats:italic>
in DAP-R
<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">E. faecium</jats:named-content>
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
<jats:italic>liaR</jats:italic>
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
<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">E. faecium</jats:named-content>
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
<jats:italic>liaR</jats:italic>
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.
</jats:p>
Subjects
bacillus-subtilis
;
staphylococcus-aureus
;
escherichia-coli
;
acridine-orange
;
susceptibility
;
faecalis
;
domains
;
nonsusceptibility
;
dye