LiaX is a surrogate marker for cell envelope stress and daptomycin non-susceptibility in Enterococcus faecium

Autores organización

• Diana Panesso Botero

  Autor

• 

  Sandra Liliana Rincon Nuñez

  Autor

• 

  Jinnethe Cristina Reyes Manrique

  Autor

Autores

• Axell-House D.B.
• Simar S.R.
• Miller W.R.
• Khan A.
• Pemberton O.A.
• Valdez L.
• Nguyen A.H.
• Hood K.S.
• Rydell K.
• Detranaltes A.M.
• Jones M.N.
• Atterstrom R.
• Sahasrabhojane P.V.
• Suleyman G.
• Zervos M.
• Shelburne S.A.
• Singh K.V.
• Shamoo Y.
• Hanson B.M.
• Tran T.T.
• Arias C.A.

Unidades de investigación

• Unidad de Genética y Resistencia Antimicrobiana UGRA

Resumen

Daptomycin (DAP) is often used as a first-line therapy to treat vancomycin-resistant Enterococcus faecium infections, but emergence of DAP non-susceptibility threatens the effectiveness of this antibiotic. Moreover, current methods to determine DAP minimum inhibitory concentrations (MICs) have poor reproducibility and accuracy. In enterococci, DAP resistance is mediated by the LiaFSR cell membrane stress response system, and deletion of liaR encoding the response regulator results in hypersusceptibility to DAP and antimicrobial peptides. The main genes regulated by LiaR are a cluster of three genes, designated liaXYZ. In Enterococcus faecalis, LiaX is surface-exposed with a C-terminus that functions as a negative regulator of cell membrane remodeling and an N-terminal domain that is released to the extracellular medium where it binds DAP. Thus, in E. faecalis, LiaX functions as a sentinel molecule recognizing DAP and controlling the cell membrane response, but less is known about LiaX in E. faecium. Here, we found that liaX is essential in E. faecium with an activated LiaFSR system. Unlike E. faecalis, E. faecium LiaX is not detected in the extracellular milieu and does not appear to alter phospholipid architecture. We further postulated that LiaX could be used as a surrogate marker for cell envelope activation and non-susceptibility to DAP. For this purpose, we developed and optimized a LiaX enzyme-linked immunosorbent assay (ELISA). We then assessed 86 clinical E. faecium bloodstream isolates for DAP MICs and used whole genome sequencing to assess for substitutions in LiaX. All DAP-resistant clinical strains of E. faecium exhibited elevated LiaX levels. Strikingly, 73% of DAP-susceptible isolates by standard MIC determination also had elevated LiaX ELISAs compared to a well-characterized DAP-susceptible strain. Phylogenetic analyses of predicted amino acid substitutions showed 12 different variants of LiaX without a specific association with DAP MIC or LiaX ELISA values. Our findings also suggest that many E. faecium isolates that test DAP susceptible by standard MIC determination are likely to have an activated cell stress response that may predispose to DAP failure. As LiaX appears to be essential for the cell envelope response to DAP, its detection could prove useful to improve the accuracy of susceptibility testing by anticipating therapeutic failure. Copyright © 2024 American Society for Microbiology. All Rights Reserved.

Keywords

• antibiotic resistance; daptomycin; Enterococcus faecium;Anti-Bacterial Agents; Biomarkers; Cell Membrane; Daptomycin; Drug Resistance, Bacterial; Enterococcus faecalis; Enterococcus faecium; Gram-Positive Bacterial Infections; Humans; Microbial Sensitivity Tests; Phylogeny; Reproducibility of Results; daptomycin; antiinfective agent; biological marker; daptomycin; amino acid substitution; amino terminal sequence; antibiotic sensitivity; Article; carboxy terminal sequence; cell membrane; cellular stress response; daptomycin resistance; disease marker; Enterococcus faecalis; Enterococcus faecium; Enterococcus faecium infection; enzyme linked immunosorbent assay; first-line treatment; in vitro study; minimum inhibitory concentration; nonhuman; phylogeny; vancomycin resistant Enterococcus; whole genome sequencing; antibiotic resistance; Enterococcus faecium; genetics; Gram positive infection; human; metabolism; microbial sensitivity test; reproducibility