title: Causal role of single nucleotide polymorphisms within the mprF gene of Staphylococcus aureus in daptomycin resistance.
abstract: Single nucleotide polymorphisms (SNPs) within the mprF open reading frame (ORF) have been commonly observed in daptomycin-resistant (DAP(r)) Staphylococcus aureus strains. Such SNPs are usually associated with a gain-in-function phenotype, in terms of either increased synthesis or enhanced translocation (flipping) of lysyl-phosphatidylglycerol (L-PG). However, it is unclear if such mprF SNPs are causal in DAP(r) strains or are merely a biomarker for this phenotype. In this study, we used an isogenic set of S. aureus strains: (i) Newman, (ii) its isogenic ΔmprF mutant, and (iii) several in trans plasmid complementation constructs, expressing either a wild-type or point-mutated form of the mprF ORF cloned from two isogenic DAP-susceptible (DAP(s))-DAP(r) strain pairs (616-701 and MRSA11/11-REF2145). Complementation of the ΔmprF strain with singly point-mutated mprF genes (mprFS295L or mprFT345A) revealed that (i) individual and distinct point mutations within the mprF ORF can recapitulate phenotypes observed in donor strains (i.e., changes in DAP MICs, positive surface charge, and cell membrane phospholipid profiles) and (ii) these gain-in-function SNPs (i.e., enhanced L-PG synthesis) likely promote reduced DAP binding to S. aureus by a charge repulsion mechanism. Thus, for these two DAP(r) strains, the defined mprF SNPs appear to be causally related to this phenotype.
authors.affiliation: Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA.
authors.forename: Soo-Jin
authors.initials: SJ
authors.lastname: Yang
authors.forename: Nagendra N
authors.initials: NN
authors.lastname: Mishra
authors.forename: Aileen
authors.initials: A
authors.lastname: Rubio
authors.forename: Arnold S
authors.initials: AS
authors.lastname: Bayer
mesh_terms: D019881:Aminoacyltransferases / Q000235:genetics* / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D017576:Daptomycin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005816:Genetic Complementation Test; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D009154:Mutation; D016366:Open Reading Frames; D020641:Polymorphism, Single Nucleotide; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D055672:Static Electricity
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D008563:Membrane Lipids; D019881:Aminoacyltransferases; C429146:mprF protein, Staphylococcus aureus; D017576:Daptomycin