These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Serial daptomycin selection generates daptomycin-nonsusceptible Staphylococcus aureus strains with a heterogeneous vancomycin-intermediate phenotype.
    Author: Camargo IL, Neoh HM, Cui L, Hiramatsu K.
    Journal: Antimicrob Agents Chemother; 2008 Dec; 52(12):4289-99. PubMed ID: 18824611.
    Abstract:
    In order to better understand the mechanism of daptomycin resistance, we generated a daptomycin-nonsusceptible derivative strain, strain 10*3d1 (MIC = 3.0 microg/ml), by in vitro exposure of methicillin-resistant Staphylococcus aureus strain N315DeltaIP (MIC = 0.5 microg/ml) to daptomycin. We also obtained a daptomycin-susceptible phenotypic revertant strain, strain 10*3d1-10 (MIC = 1.0 microg/ml), by passaging 10*3d1 in drug-free medium for 10 days. The resultant triple-isogenic strains were analyzed for their phenotypes and gene expression by microarray analysis. No significant differences in the membrane fluidities of 10*3d1 and 10*3d1-10 compared to the membrane fluidity of N315DeltaIP were observed. Resistant strain 10*3d1 had the highest membrane potential, followed by strains 10*3d1-10 and N315DeltaIP. The vancomycin and teicoplanin MICs also increased. Teichoic acid genes (tagA, tagG), mprF encoding lysyl-phosphatidylglycerol, and cls encoding cardiolipin synthase were downregulated in 10*3d1 and 10*3d1-10. The vraF and vraG genes, which encode ATP binding cassette transporter proteins, were upregulated in 10*3d1. The vraSR two-component regulatory system was upregulated, and electron microscopy revealed that the cell wall of 10*3d1 was significantly thicker than that of the parental strain. Taken together, daptomycin exposure selected a daptomycin-nonsusceptible strain with a phenotype similar to that of heterogeneous vancomycin-intermediate S. aureus and a transcription profile that partially overlapped that of heterogeneous vancomycin-intermediate S. aureus.
    [Abstract] [Full Text] [Related] [New Search]