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Quality of molecular detection of vancomycin resistance in enterococci: results of 6 consecutive years of Quality Control for Molecular Diagnostics (QCMD) external quality assessment

  • Veerle MatheeussenEmail author
  • Katherine Loens
  • Calum Scott
  • Caterina Di Lorenzo
  • Elaine McCulloch
  • Oliver Donoso Mantke
  • Herman Goossens
  • Paul Wallace
  • Margareta Ieven
Original Article

Abstract

The quality of PCR to detect vancomycin-resistant enterococci (VRE) was evaluated by analysing their performance in six consecutive external quality assessment (EQA) schemes, organized annually since 2013 by Quality Control for Molecular Diagnostics. VRE EQA panels consisted of 12–14 heat-inactivated samples. Sensitivity was tested with vanA-positive Enterococcus faecium (E. faecium), vanB-positive E. faecium, E. faecalis or E. gallinarum or vanC-positive E. gallinarum in different concentrations. Vancomycin-susceptible enterococci, Staphylococcus aureus or sample matrix was used to study the specificity. Participants were asked to report the VRE resistance status of each sample. The detection rate of vanA-positive samples was already 95% in the 2013 EQA panel (range 94–97%) and remained stable over the years. The 2013 detection rate of vanB-positive samples was 82% but increased significantly by more than 10% in subsequent years (96% in 2014, 95% in 2015, 92% in 2016 and 93% in 2017/2018, p < 0.05). The vanC detection rate by the limited number of assays specifically targeting this gene was lower compared to vanA/B (range 55–89%). The number of false positives in the true-negative sample (8% in 2013 to 1.4% in 2018) as well as the van-gene-negative bacterial samples (4% in 2013 to 0% in 2018) declined over the years. In the six years of VRE proficiency testing to date, the detection of vanA-positive strains was excellent and an increased sensitivity in vanB detection as well as an increase in specificity was observed. Commercial and in-house assays performed equally well.

Keywords

VRE Proficiency testing Vancomycin resistance Molecular diagnostics 

Notes

Acknowledgments

IOWA1 and IOWA2 were kindly provided by Ronald N. Jones, MD, University of Iowa College of Medicine Iowa City, Iowa, USA.

Funding

The National Reference Centre for Vancomycin-resistant enterococci is partially supported by the Belgian Ministry of Social affairs through a fund within the Health Insurance System.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Veerle Matheeussen
    • 1
    • 2
    • 3
    Email author
  • Katherine Loens
    • 1
    • 2
  • Calum Scott
    • 4
  • Caterina Di Lorenzo
    • 4
  • Elaine McCulloch
    • 4
  • Oliver Donoso Mantke
    • 4
  • Herman Goossens
    • 1
    • 2
  • Paul Wallace
    • 4
  • Margareta Ieven
    • 1
    • 2
  1. 1.Department of Microbiology, National Reference Centre for Vancomycin-resistant EnterococciUniversity Hospital AntwerpEdegemBelgium
  2. 2.Department of Medical Microbiology, Vaccine & Infectious Disease Institute (VAXINFECTIO)University of AntwerpWilrijkBelgium
  3. 3.Department of Medical BiochemistryUniversity of AntwerpWilrijkBelgium
  4. 4.Quality Control for Molecular Diagnostics (QCMD)GlasgowUK

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