Oral Presentation 20th Lancefield International Symposium on Streptococci and Streptococcal Diseases 2017

Four consecutive multicenter external quality assessments to assess the quality of molecular amplification methods for the detection of vancomycin resistant enterococci   (#44)

Margareta Ieven 1 2 , Katherine Loens 2 , Calum Scott 1 , Caterina Di Lorenzo 1 , Elaine McCulloch 1 , Paul Wallace 1
  1. QCMD, Glasgow, Scotland, UK
  2. University Hospital Antwerp, University of Antwerp, Antwerp, Belgium


The QCMD vancomycin resistant enterococci (VRE) pilot EQA study was introduced in 2013 and repeated yearly to assess the ability of laboratories to correctly detect and characterize vanA, vanB and vanC genes in VRE by molecular methods.


Methods: EQA panels contained samples with VRE at dilutions between 1.0x103 and 1.0x107 CFU/ml, one mixture of vanB and vanC positive VRE, vancomycin susceptible enterococci and an Enterococcus negative sample.


Results: The number of participants increased from 44 laboratories in 16 countries to 65 laboratories in 21 countries. The majority of results were generated using in-house developed assays: 74.4% (29/39), 70.3% (26/37), 63.3% (31/49) and 55.2% (37/67) from 2013 to 2016 . This represents an increase in the proportion of commercial assays used in these EQA studies from 25.6% in 2013 to 44.7% in 2016.

In all EQA’s participants could correctly determine the presence of vanA in ≥ 92.3%. The correct detection of vanB increased from 71.8-87.2%  of datasets in 2013 to 86.6-95.5% of datasets in 2016.  Detection and characterization of vanC genes ranged from 14.3% to 35.9%. False positivity rate decreased from 7.7% in 2013 to 1.5% in 2016.

Conclusion: The majority of participating labs returned results generated by in-house PCRs but commercially available kits are increasingly used. Most participants were able to correctly characterize the vanA or vanB vancomycin resistance genes. The detection of the vanC genes is not included in the majority of commercially available or in-house tests explaining the poor results on EQA samples containing vanC genes.