title: VraSR two-component regulatory system contributes to mprF-mediated decreased susceptibility to daptomycin in in vivo-selected clinical strains of methicillin-resistant Staphylococcus aureus.
abstract: Daptomycin (DAP) is a new class of cyclic lipopeptide antibiotic highly active against methicillin-resistant Staphylococcus aureus (MRSA) infections. Proposed mechanisms involve disruption of the functional integrity of the bacterial membrane in a Ca-dependent manner. In the present work, we investigated the molecular basis of DAP resistance in a group of isogenic MRSA clinical strains obtained from patients with S. aureus infections after treatment with DAP. Different point mutations were found in the mprF gene in DAP-resistant (DR) strains. Investigation of the mprF L826F mutation in DR strains was accomplished by inactivation and transcomplementation of either full-length wild-type or mutated mprF in DAP-susceptible (DS) strains, revealing that they were mechanistically linked to the DR phenotype. However, our data suggested that mprF was not the only factor determining the resistance to DAP. Differential gene expression analysis showed upregulation of the two-component regulatory system vraSR. Inactivation of vraSR resulted in increased DAP susceptibility, while complementation of vraSR mutant strains restored DAP resistance to levels comparable to those observed in the corresponding DR wild-type strain. Electron microscopy analysis showed a thicker cell wall in DR CB5012 than DS CB5011, an effect that was related to the impact of vraSR and mprF mutations in the cell wall. Moreover, overexpression of vraSR in DS strains resulted in both increased resistance to DAP and decreased resistance to oxacillin, similar to the phenotype observed in DR strains. These results support the suggestion that, in addition to mutations in mprF, vraSR contributes to DAP resistance in the present group of clinical strains.
authors: Division of Infectious Diseases, Department of Internal Medicine, Virginia Commonwealth University, Richmond, Virginia, USA.
authors: Shrenik
authors: S
authors: Mehta
authors: Arabela X
authors: AX
authors: Cuirolo
authors: Konrad B
authors: KB
authors: Plata
authors: Sarah
authors: S
authors: Riosa
authors: Jared A
authors: JA
authors: Silverman
authors: Aileen
authors: A
authors: Rubio
authors: Roberto R
authors: RR
authors: Rosato
authors: Adriana E
authors: AE
authors: Rosato
mesh_terms: D019881:Aminoacyltransferases / Q000235:genetics* / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002473:Cell Wall / Q000187:drug effects / Q000648:ultrastructure; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics; D017576:Daptomycin / Q000494:pharmacology*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D005816:Genetic Complementation Test; D005838:Genotype; D006801:Humans; D016106:Methicillin Resistance / Q000187:drug effects; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics* / Q000648:ultrastructure; D008854:Microscopy, Electron; D009154:Mutation; D010641:Phenotype; D010957:Plasmids; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology; D059467:Transcriptome / Q000187:drug effects / Q000235:genetics; D014169:Transformation, Bacterial
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C478170:VraR protein, Staphylococcus aureus; C478169:VraS protein, Staphylococcus aureus; D019881:Aminoacyltransferases; C429146:mprF protein, Staphylococcus aureus; D017576:Daptomycin