Comparability of antimicrobial susceptibility test results from 22 European countries and Israel: An external quality assurance exercise of the European antimicrobial resistance surveillance system (EARSS) in collaboration with the United Kingdom national external quality assurance scheme (UK NEQAS)

S. Bronzwaer*, U. Buchholz, P. Courvalin, J. Snell, G. Cornaglia, A. de Neeling, H. Aubry-Damon, J. Degener, H. Mittermayer, W. Koller, H. Goossens, F. van Loock, B. Markova, P. Urbaskova, T. L. Sørensen, D. Monnet, P. Huovinen, O. Lyytikäinen, P. Courvalin, H. Aubry-DamonW. Witte, T. Breuer, N. Legakis, G. Vatopoulos, M. Konkoly-Thege, K. Kristinsson, H. Briem, O. Murphy, D. O'Flanagan, R. Raz, G. Cornaglia, M. L. Moro, R. Hemmer, M. Borg, A. de Neeling, W. Goettsch, E. Hoiby, P. Aavitsland, V. Hryniewicz, M. Caniça, M. Paixao, M. Gubina, F. Baquero, J. Campos, B. Olsson-Liljequist, O. Cars, Alan Johnson, M. Wale

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)


The goal ot this exercise was to organize external quality assurance (QA) of antibiotic susceptibility testing for laboratories participating in EARSS and to assess the comparability of susceptibility test results across countries, and guidelines. In September 2000, UK NEQAS distributed a set of three Streptococcus pneumoniae strains, two Staphylococcus aureus strains and one Streptococcus haemolyticus strain. Laboratories reported the guideline followed, the interpretation of the susceptibility test result and the MIC, if tested. In this study we considered results 'concordant' if the reported interpretation ot the participating laboratory agreed with the designated interpretation of reference laboratories. Overall, 433 (92%) of 471 laboratories from 23 countries reported back. Of the 8685 tests that were assessed, 8322 (96%) were interpreted correctly by the participants. Concordance tor detection of penicillin non-susceptibility in the three S. pneumoniae strains was 96%, 90% and 87%, respectively. Laboratories performed extremely well in detecting oxacillin resistance in the homogeneously methicillin-resistant S. aureus (MRSA) strain, but the concordance rate dropped from 100% to 77% in the heterogeneously resistant MRSA strain. Concordance for detection of teicoplanin resistance in the S. haemolyticus strain was 82%. We stratified concordance rates first for country and then for guideline used, but observed only minor differences among countries and guidelines. Quantitative methods yielding an MIC were more concordant than non-MIC methods tor penicillin resistance in the S. pneumoniae strains (94% versus 79%). The NCCLS guideline was the most frequently followed, by 61 % of laboratories trom 19 countries. This exercise shows that, overall, countries participating in EARSS are capable ot delivering susceptibility data of good quality. The comparability ot susceptibility data for penicillin resistance in S. pneumoniae and for homogeneous methicillin resistance in S. aureus is satistactory among European countries and across guidelines. However, we emphasize the importance of determining an MIC tor suspected penicillin non-susceptible S. pneumoniae and for suspected glycopeptide non-susceptible S. aureus. Laboratories, particularly in some countries, may need to improve their capability to detect oxacillin resistance in heterogeneously resistant MRSA. For continuous external quality assessment we recommend that laboratories participate in national and international schemes with frequent distribution ot control strains.

Original languageEnglish
Pages (from-to)953-964
Number of pages12
JournalJournal of Antimicrobial Chemotherapy
Issue number6
Publication statusPublished - 1 Dec 2002

Bibliographical note

Funding Information:
We express our thanks and appreciation for the organization by UK NEQAS, for the countries’ co-ordinating centres who distributed the strains swiftly and for the overwhelmingly good response rate of the 471 laboratories participating in EARSS. We thank N. Nagelkerke for help in the statistical analysis and thank the national representatives of EARSS in the participating countries. We also welcome the comments on this article by D. Brown and G. Kahlmeter from EUCAST. EARSS is funded by the European Commission, DG SANCO [Agreement SI2.123794 (99CVF4-018) European Antimicrobial Resistance Surveillance System (EARSS)]. Participating countries and national representatives in EARSS during 2000: Austria, H. Mittermayer, W. Koller; Belgium, H. Goossens, F. van Loock; Bulgaria, B. Markova; Czech Republic, P. Urbaskova; Denmark, T. L. Sørensen, D. Monnet; Finland, P. Huovinen, O. Lyytikäinen; France, P. Courvalin, H. Aubry-Damon; Germany, W. Witte, T. Breuer; Greece, N. Legakis, G. Vatopoulos; Hungary, M. Konkoly-Thege; Iceland, K. Kristinsson, H. Briem; Ireland, O. Murphy, D. O’Flanagan; Israel, R. Raz; Italy, G. Cornaglia, M. L. Moro; Luxembourg, R. Hemmer; Malta, M. Borg; Netherlands, A. de Neeling, W. Goettsch; Norway, E. Hoiby, P. Aavitsland; Poland, V. Hryniewicz; Portugal, M. Caniça, M. Paixao; Slovenia, M. Gubina; Spain, F. Baquero, J. Campos; Sweden, B. Olsson-Liljequist, O. Cars; United Kingdom, A. Johnson, M. Wale.


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