International quality assurance study for characterization of Streptococcus pyogenes

Shona Neal*, Bernard Beall, Kim Ekelund, Birgitta Henriques-Normark, Aftab Jasir, Dwight Johnson, Edward Kaplan, Marguerite Lovgren, Ralf Rene Reinert, Androulla Efstratiou, H. Goosens, G. Tyrrell, L. Strakova, M. Staum Kaltoft, J. Vuopio-Varkila, L. Mihaila-Amrouche, M. Van Der Linden, L. Zachariadou, J. Papaparaskevas, L. ValinskyR. Creti, W. Wannet, D. Martin, M. Straut, C. Schalén, B. Luca, J. Darenberg, A. Tanna, V. Sakota

*Corresponding author for this work

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11 Citations (Scopus)


Surveillance of group A streptococcal (GAS) infections was undertaken as a major component of the European Commission-funded project on severe GAS disease in Europe (strep-EURO). One aim of strep-EURO was to improve the quality of GAS characterization by standardization of methods. An external quality assurance study (EQA) was therefore carried out to evaluate current global performance. Eleven strep-EURO and seven other streptococcal reference centers received a panel of 20 coded GAS isolates for typing. Conventional phenotypic typing (based on cell surface T and M protein antigens and opacity factor [OF] production) and molecular methods (emm gene typing) were used either as single or combined approaches to GAS typing. T typing was performed by 16 centers; 12 centers found one or more of the 20 strains nontypeable (typeability, 89%), and 11 centers reported at least one incorrect result (concordance, 93%). The 10 centers that tested for OF production achieved 96% concordance. Limited availability of antisera resulted in poor typeability values from the four centers that performed phenotypic M typing (41%), three of which also performed anti-OF typing (typeability, 63%); however, concordance was high for both M (100%) and anti-OF (94%) typing. In contrast, the 15 centers that performed emm gene sequencing achieved excellent typeability (97%) and concordance (98%), although comparison of the performance between centers yielded typeability rates from 65 to 100% and concordance values from 83 to 100%. With the rapid expansion and use of molecular genotypic methods to characterize GAS, continuation of EQA is essential in order to achieve international standardization and comparison of type distributions.

Original languageEnglish
Pages (from-to)1175-1179
Number of pages5
JournalJournal of Clinical Microbiology
Issue number4
Publication statusPublished - Apr 2007


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