A liaR Deletion Restores Susceptibility to Daptomycin and Antimicrobial Peptides in Multidrug-Resistant Enterococcus faecalis

Abstract

Daptomycin is a lipopeptide antibiotic that is used clinically against many gram-positive bacterial pathogens and is considered a key frontline bactericidal antibiotic to treat multidrug-resistant enterococci. Emergence of daptomycin resistance during therapy of serious enterococcal infections is a major clinical issue. In this work, we show that deletion of the gene encoding the response regulator, LiaR (a member of the LiaFSR system that controls cell envelope homeostasis), from daptomycin-resistant Enterococcus faecalis not only reversed resistance to 2 clinically available cell membrane-targeting antimicrobials (daptomycin and telavancin), but also resulted in hypersusceptibility to these antibiotics and to a variety of antimicrobial peptides of diverse origin and with different mechanisms of action. The changes in susceptibility to these antibiotics and antimicrobial peptides correlated with in vivo attenuation in a Caenorhabditis elegans model. Mechanistically, deletion of liaR altered the localization of cardiolipin microdomains in the cell membrane. Our findings suggest that LiaR is a master regulator of the enterococcal cell membrane response to diverse antimicrobial agents and peptides; as such, LiaR represents a novel target to restore the activity of clinically useful antimicrobials against these organisms and, potentially, increase susceptibility to endogenous antimicrobial peptides.

A Novel Phosphodiesterase of the GdpP Family Modulates Cyclic di-AMP Levels in Response to Cell Membrane Stress in Daptomycin-Resistant Enterococci

“…As c-di-AMP signaling has not been previously identified in enterococci, it was essential to test whether c-di-AMP was present at levels consistent with its being a second messenger in vivo. Thus, we measured c-di-AMP in E. faecalis S613 and its daptomycin-resistant derivative E. faecalis R712, a vancomycin-resistant strain pair isolated from the bloodstream of a patient before and after daptomycin treatment, respectively (14,41). Additionally, we included a laboratory strain of E. faecalis, OG1RF (Table 1) (14,25).…”

Fosfomycin Enhances the Activity of Daptomycin against Vancomycin-Resistant Enterococci in an In Vitro Pharmacokinetic-Pharmacodynamic Model

“…The addition of fosfomycin resulted in a further reduction of cell surface charge, which is a plausible explanation for the enhanced killing demonstrated when combined with daptomycin. VRE resistance to daptomycin has previously been linked to genetic changes in genes that regulate cell envelope homeostasis and membrane lipid metabolism (liaFSR, yycFG, cls, and cfa); however, there appears to be a variety of genetic pathways to daptomycin nonsusceptibility (49)(50)(51)(52)(53)(54)(55). In addition to altered cell surface charge, an alternative mechanism that has been proposed is related to redistribution of membrane lipids that drive daptomy-cin binding away from division septa, where it is believed to be more devastating to the organism (53,55,56).…”

Stress Physiology of Lactic Acid Bacteria

“…This deletion also restored susceptibility to daptomycin and telavancin, antibiotics that disrupt the cell membrane, in a multidrug-resistant E. faecalis strain (450).…”