gms | German Medical Science

Bad Honnef-Symposium 2019

Paul-Ehrlich-Gesellschaft für Chemotherapie (PEG e. V.)

29. - 30.04.2019, Bonn

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Comparison of Vitek 2, three different gradient strip tests and broth microdilution in detecting vanB-positive Enterococcus faecium isolates with low vancomycin MICs

Meeting Abstract

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  • Ingo Klare - National Reference Centre for Staphylococci and Enterococci (NRC), Division Nosocomial Pathogens and Antibiotic Resistances
  • Jennifer K. Bender - National Reference Centre for Staphylococci and Enterococci (NRC), Division Nosocomial Pathogens and Antibiotic Resistances
  • Carola Fleige - National Reference Centre for Staphylococci and Enterococci (NRC), Division Nosocomial Pathogens and Antibiotic Resistances
  • Nancy Kriebel - National Reference Centre for Staphylococci and Enterococci (NRC), Division Nosocomial Pathogens and Antibiotic Resistances
  • Axel Hamprecht - Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany and DZIF (German Centre for Infection Research), partner site Bonn-Cologne, Germany
  • Sören Gatermann - Department of Medical Microbiology, Institute for Medical Microbiology and Hygiene, Ruhr University Bochum, Bochum, Germany
  • Guido Werner - National Reference Centre for Staphylococci and Enterococci (NRC), Division Nosocomial Pathogens and Antibiotic Resistances

Bad Honnef-Symposium 2019. Bonn, 29.-30.04.2019. Düsseldorf: German Medical Science GMS Publishing House; 2019. Doc19bhs12

doi: 10.3205/19bhs12, urn:nbn:de:0183-19bhs128

Published: April 25, 2019

© 2019 Klare et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at http://creativecommons.org/licenses/by/4.0/.

Outline

Text

Objectives: EUCAST issued a warning regarding less reliable gradient strip tests for confirming vancomycin resistance in enterococci. We aimed at comparing performance of various diagnostic standard and confirmatory tests to identify and determine vanB-type vancomycin resistance in the most reliable manner.

Methods: We established a strain collection of vanB-positive E. faecium isolates (n=80) which became noticeable by low level vancomycin MICs in previous standard diagnostic assays. We compared the performance of bioMerieux’s Vitek 2, of broth microdilution and of three different gradient strip test providers (Oxoid, Liofilchem, bioMerieux). For the latter we compared the standard procedure vs. the “macromethod”.

Results: Vitek 2 identified 76% of vanB-VRE. Using broth microdilution only 60% of vanB-VRE were correctly diagnosed. Results of the three gradient strip tests were similar and lead to a sensitivity of 35–41% only. Using the “macromethod” substantially improved performance of all strip tests leading to a maximum/best performance after 48h readout by reaching a sensitivity of 88–96%.

Conclusions: We recommend specifying the EUCAST warning for gradient strip tests to especially demand the “macromethod” and suggest a prolonged incubation time of up to 48h and a second readout.

The study was performed under the auspices of the Section Basics of the Paul Ehrlich Society for Chemotherapy.