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Quantifying the matrix of relationships between reduced vancomycin susceptibility phenotypes and outcomes among

T P Lodise1, G L Drusano2, V Lazariu3

  • 1Albany College of Pharmacy and Health Sciences, 106 New Scotland Avenue, Albany, NY, USA thomas.lodise@acphs.edu.

The Journal of Antimicrobial Chemotherapy
|May 21, 2014
PubMed
Abstract

Insights

Reduced vancomycin susceptibility phenotypes (rVSPs) in methicillin-resistant Staphylococcus aureus (MRSA) infections increase treatment failure. The more rVSP markers present, the higher the likelihood of adverse outcomes in patients treated with vancomycin.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Pharmacology

Background:

  • Phenotypic characteristics of Staphylococcus aureus, termed reduced vancomycin susceptibility phenotypes (rVSPs), are linked to poor outcomes in vancomycin-treated patients.
  • The combined impact of these rVSPs on treatment outcomes is not fully understood.

Purpose of the Study:

  • To investigate the interrelationship between rVSPs in methicillin-resistant S. aureus (MRSA).
  • To assess the individual and combined effects of rVSPs on treatment outcomes in patients with MRSA bloodstream infections receiving vancomycin.

Main Methods:

  • An observational study included adult, hospitalized patients with MRSA bloodstream infections treated with vancomycin (January 2005 - June 2009).
  • Evaluated rVSPs included Etest MIC, broth microdilution MIC, MBC:MIC ratio, and vancomycin heteroresistance.
  • Treatment failure was defined by 30-day mortality, persistent bacteremia (≥7 days), or recurrence within 60 days.

Main Results:

  • Of 184 patients, 41.3% experienced treatment failure.
  • A linear exposure-response relationship was observed between the number of rVSP markers and adverse outcomes.
  • Increasing numbers of rVSP phenotypes correlated with a 10%-18% incremental increase in overall failure rates.

Conclusions:

  • The findings suggest that reduced vancomycin susceptibility phenotypes contribute to adverse treatment outcomes in a combined manner.
  • rVSPs act in concert to negatively impact vancomycin treatment efficacy for MRSA infections.
Keywords:
S. aureusbacteraemiamethicillin-resistant Staphylococcus aureus

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