title: Heterogeneity of mprF sequences in methicillin-resistant Staphylococcus aureus clinical isolates: role in cross-resistance between daptomycin and host defense antimicrobial peptides.
abstract: Over the past several years, single-nucleotide polymorphisms (SNPs) within the mprF open reading frame (ORF) have been proposed to be associated with a gain-of-function phenotype in terms of daptomycin (DAP) nonsusceptibility (referred to as daptomycin resistance [DAP-R] herein for ease of presentation) in Staphylococcus aureus. We investigated the frequencies of SNPs within the mprF ORF and the relationships of such SNPs to cross-resistance between DAP and cationic host defense peptides (HDPs). Thirty-five well-characterized, unique DAP-susceptible (DAP-S) and DAP-R methicillin-resistant S. aureus (MRSA) isolates of the clonal complex 5 genotype were used. In addition to mprF SNPs and DAP-HDP cross-resistance, several other key genotypic and phenotypic metrics often associated with DAP-R were delineated, as follows: (i) mprF expression, (ii) membrane phospholipid content, (iii) positive surface charge, (iv) DAP binding, and (v) cell wall thickness profiles. A number of DAP-S strains (MICs of ≤ 1 μg/ml) exhibited mprF SNPs, occasionally with high-level mprF sequence variation from the genotype reference strain. However, none of these SNPs were localized to well-chronicled mprF hot spot locations associated with DAP-R in S. aureus. In contrast, all 8 DAP-R isolates demonstrated SNPs within such known mprF hot spots. Moreover, only the DAP-R strains showed MprF gain-of-function phenotypes, enhanced mprF expression, higher survival against two prototypical HDPs, and reduced DAP binding. Although a heterogenous array of mprF SNPs were often found in DAP-S strains, only selected hot spot SNPs, combined with concurrent mprF dysregulation, were associated with the DAP-R phenotype.
authors.affiliation: Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA The David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Arnold S
authors.initials: AS
authors.lastname: Bayer
authors.affiliation: Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA The David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Nagendra N
authors.initials: NN
authors.lastname: Mishra
authors.affiliation: University of California, San Diego School of Medicine, La Jolla, California, USA Department of Medicine, Sharp Memorial Hospital, San Diego, California, USA.
authors.forename: George
authors.initials: G
authors.lastname: Sakoulas
authors.affiliation: University of California, San Diego School of Medicine, La Jolla, California, USA.
authors.forename: Poochit
authors.initials: P
authors.lastname: Nonejuie
authors.affiliation: The David Geffen School of Medicine at UCLA, Los Angeles, California, USA Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Cynthia C
authors.initials: CC
authors.lastname: Nast
authors.affiliation: University of California, San Diego School of Medicine, La Jolla, California, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Pogliano
authors.affiliation: Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA.
authors.forename: Kuan-Tsen
authors.initials: KT
authors.lastname: Chen
authors.affiliation: Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA.
authors.forename: Steven N
authors.initials: SN
authors.lastname: Ellison
authors.affiliation: Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA The David Geffen School of Medicine at UCLA, Los Angeles, California, USA Division of Molecular Medicine, Harbor-UCLA Medical Center, Torrance, California, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Yeaman
authors.affiliation: Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA The David Geffen School of Medicine at UCLA, Los Angeles, California, USA sjyang@ucla.edu.
authors.forename: Soo-Jin
authors.initials: SJ
authors.lastname: Yang
mesh_terms: D019881:Aminoacyltransferases / Q000235:genetics* / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002473:Cell Wall / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D002999:Clone Cells; D017576:Daptomycin / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D013203:Staphylococcal Infections / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D001426:Bacterial Proteins; D010743:Phospholipids; D019881:Aminoacyltransferases; C429146:mprF protein, Staphylococcus aureus; D017576:Daptomycin