In vitro activities of Daptomycin, Linezolid, and Quinupristin-Dalfopristin against a challenge panel of Staphylococci and Enterococci, including vancomycin-intermediate staphylococcus aureus and vancomycin-resistant Enterococcus faecium

Microb Drug Resist. 2003 Winter;9(4):389-93. doi: 10.1089/107662903322762833.


We assessed the in vitro activities of daptomycin, linezolid, and quinupristin-dalfopristin (QD) against a contemporary challenge panel of 88 staphylococcal and 90 enterococcal isolates. The staphylococci selected included vancomycin-intermediate Staphylococcus aureus (VISA), methicillin-resistant S. aureus, and coagulasenegative staphylococci. Enterococcal isolates included vancomycin-resistant Enterococcus faecium (VREF) containing either vanA, vanB1, or vanD. The MICs of daptomycin, linezolid, and QD were determined using commercial broth microdilution panels. All three VISA isolates were susceptible to daptomycin, linezolid, and QD. QD was the most active agent against staphylococcal isolates (MIC50 < or = 0.5 microg/ml and MIC90 = 1 microg/ml), including those with decreased susceptibility to vancomycin. QD was also the most active agent against VREF (MIC90 < or = 0.5 microg/ml). No differences were seen for susceptibility of vanA, vanB1, and vanD VREF strains for daptomycin, linezolid, or QD. Daptomycin was the most effective against E. faecalis. On the basis of manufacturer-suggested interpretive criteria, 92% of isolates were susceptible (MIC90 = 4 microg/ml). All isolates tested were susceptible to at least one antimicrobial agent for which interpretive criteria have been defined. Population analysis of three S. aureus isolates for which the daptomycin MICs were 8 microg/ml showed a pattern of homogeneous resistance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetamides / pharmacology*
  • Anti-Bacterial Agents / pharmacology*
  • Anti-Infective Agents / pharmacology*
  • Daptomycin / pharmacology*
  • Drug Therapy, Combination / pharmacology*
  • Enterococcus faecium / drug effects*
  • Genes, Bacterial / genetics
  • Linezolid
  • Methicillin Resistance
  • Microbial Sensitivity Tests
  • Oxazolidinones / pharmacology*
  • Staphylococcus aureus / drug effects*
  • Staphylococcus aureus / genetics
  • Vancomycin Resistance* / genetics
  • Virginiamycin / pharmacology*


  • Acetamides
  • Anti-Bacterial Agents
  • Anti-Infective Agents
  • Oxazolidinones
  • Virginiamycin
  • quinupristin-dalfopristin
  • Linezolid
  • Daptomycin