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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

API 20 strep identification system may incorrectly speciate enterococci with low level resistance to vancomycin

Lisa G Winston1, Szekim Pang, Barbara L Haller

  • 1Department of Medicine, Division of Infectious Diseases, University of California, San Francisco/San Francisco General Hospital, San Francisco, CA 94110, USA. lisaw@itsa.ucsf.edu

Diagnostic Microbiology and Infectious Disease
|April 6, 2004
PubMed

Insights

The API 20 Strep system inaccurately identified enterococci with low-level vancomycin resistance. Most isolates, initially classified as Enterococcus faecium, required further testing for correct species identification.

Area of Science:

  • Clinical microbiology
  • Antimicrobial resistance

Background:

  • Accurate bacterial speciation is crucial for effective treatment, especially for resistant strains.
  • Enterococci are common causes of healthcare-associated infections, with vancomycin resistance being a significant concern.

Purpose of the Study:

  • To evaluate the accuracy of the API 20 Strep system for identifying enterococcal isolates with low-level vancomycin resistance.
  • To determine the reliability of this system when faced with antimicrobial resistance.

Main Methods:

  • API 20 Strep system was used for speciation.
  • 46 enterococcal isolates with vancomycin Minimum Inhibitory Concentrations (MICs) of 16-32 microg/mL were tested.
  • Further confirmatory testing was performed on discrepant results.

Main Results:

  • All 46 isolates were initially identified as Enterococcus faecium by the API 20 Strep system.
  • Subsequent testing revealed that 42 out of 46 isolates (91.3%) were incorrectly identified.
  • The API 20 Strep system showed poor performance in correctly speciating these vancomycin-resistant enterococci.

Conclusions:

  • The API 20 Strep system is unreliable for the accurate speciation of enterococci exhibiting low-level vancomycin resistance.
  • Relying solely on the API 20 Strep system can lead to misidentification and potentially inappropriate clinical management.
  • Additional diagnostic methods are necessary for reliable identification of vancomycin-resistant enterococci.

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