title: Failures in clinical treatment of Staphylococcus aureus Infection with daptomycin are associated with alterations in surface charge, membrane phospholipid asymmetry, and drug binding.
abstract: Increasingly frequent reports have described the in vivo loss of daptomycin susceptibility in association with clinical treatment failures. The mechanism(s) of daptomycin resistance is not well understood. We studied an isogenic set of Staphylococcus aureus isolates from the bloodstream of a daptomycin-treated patient with recalcitrant endocarditis in which serial strains exhibited decreasing susceptibility to daptomycin. Since daptomycin is a membrane-targeting lipopeptide, we compared a number of membrane parameters in the initial blood isolate (parental) with those in subsequent daptomycin-resistant strains obtained during treatment. In comparison to the parental strain, resistant isolates demonstrated (i) enhanced membrane fluidity, (ii) increased translocation of the positively charged phospholipid lysyl-phosphotidylglycerol to the outer membrane leaflet, (iii) increased net positive surface charge (P < 0.05 versus the parental strain), (iv) reduced susceptibility to daptomycin-induced depolarization, permeabilization, and autolysis (P < 0.05 versus the parental strain), (v) significantly lower surface binding of daptomycin (P < 0.05 versus the parental strain), and (vi) increased cross-resistance to the cationic antimicrobial host defense peptides human neutrophil peptide 1 (hNP-1) and thrombin-induced platelet microbicidal protein 1 (tPMP-1). These data link distinct changes in membrane structure and function with in vivo development of daptomycin resistance in S. aureus. Moreover, the cross-resistance to hNP-1 and tPMP-1 may also impact the capacity of these daptomycin-resistant organisms to be cleared from sites of infection, particularly endovascular foci.
authors.affiliation: Los Angeles Biomedical Research Institute at Harbor-UCLA, 1124 West Carson Street, Bldg. RB2, Room 225, Torrance, CA 90502, USA.
authors.forename: Tiffanny
authors.initials: T
authors.lastname: Jones
authors.forename: Michael R
authors.initials: MR
authors.lastname: Yeaman
authors.forename: George
authors.initials: G
authors.lastname: Sakoulas
authors.forename: Soo-Jin
authors.initials: SJ
authors.lastname: Yang
authors.forename: Richard A
authors.initials: RA
authors.lastname: Proctor
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Sahl
authors.forename: Jacques
authors.initials: J
authors.lastname: Schrenzel
authors.forename: Yan Q
authors.initials: YQ
authors.lastname: Xiong
authors.forename: Arnold S
authors.initials: AS
authors.lastname: Bayer
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology / Q000627:therapeutic use; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D002463:Cell Membrane Permeability; D017576:Daptomycin / Q000378:metabolism / Q000494:pharmacology / Q000627:therapeutic use; D024881:Drug Resistance, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D010743:Phospholipids / Q000032:analysis; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects*; D017211:Treatment Failure
chemical_list: D000900:Anti-Bacterial Agents; D010743:Phospholipids; D017576:Daptomycin