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A 1.5 Hour Procedure for Identification of Enterococcus Species Directly from Blood Cultures
05:02

A 1.5 Hour Procedure for Identification of Enterococcus Species Directly from Blood Cultures

Published on: February 10, 2011

Difficulties in detection and identification of Enterococcus faecium with low-level inducible resistance to

S Pendle1, P Jelfs, T Olma

  • 1Centre for Infectious Diseases and Microbiology, Institute of Clinical Pathology and Medical Research, Westmead Hospital, Westmead, Westmead, New South Wales, Australia. stella.pendle@symbionhealth.com

Clinical Microbiology and Infection : the Official Publication of the European Society of Clinical Microbiology and Infectious Diseases
|October 11, 2008
PubMed

Insights

Routine screening methods failed to detect a vancomycin-resistant Enterococcus faecium (VRE) strain with inducible resistance. Improved laboratory identification and surveillance are crucial to prevent VRE transmission in healthcare settings.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Clinical Laboratory Science

Background:

  • Vancomycin-resistant Enterococcus faecium (VRE) poses a significant challenge in healthcare settings.
  • Low-level, inducible vancomycin resistance in VRE can evade standard detection methods.
  • Difficulties in identifying VRE led to its undetected spread and delayed patient management.

Purpose of the Study:

  • To evaluate and compare the performance of different laboratory identification systems for a challenging VRE strain.
  • To assess the effectiveness of standard screening methods in detecting VRE with inducible resistance.
  • To identify improved methods for VRE detection and surveillance.

Main Methods:

  • Comparison of three automated identification systems: VITEK 2, API Rapid ID 32 Strep, and Phoenix 100.
  • Evaluation of CLSI disk diffusion and Etest for vancomycin susceptibility testing.
  • Optimization of VRE screening media by reducing vancomycin concentration.
  • Molecular characterization using PCR for vanB genotype and pulsed-field gel electrophoresis for strain typing.

Main Results:

  • VITEK 2 showed poor identification accuracy for the VRE strain.
  • API Rapid ID 32 Strep and Phoenix 100 demonstrated better identification capabilities.
  • Initial susceptibility testing by disk diffusion suggested vancomycin susceptibility in some isolates.
  • Reduced vancomycin concentration in screening media significantly improved VRE detection sensitivity.
  • All isolates were confirmed as vanB2/3 genotype VRE and were indistinguishable by PFGE.

Conclusions:

  • Standard laboratory identification and screening methods are inadequate for detecting VRE with low-level inducible resistance.
  • Optimized screening protocols and advanced identification systems are necessary for effective VRE surveillance.
  • Improved diagnostic strategies are essential to prevent VRE transmission and ensure timely patient care.

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