International Quality Assurance Study for Characterization of Streptococcus pyogenes

• Published in: Journal of Clinical Microbiology 2007-04, Vol.45 (4), p.1175-1179
• Main Authors: Neal, Shona, Beall, Bernard, Ekelund, Kim, Henriques-Normark, Birgitta, Jasir, Aftab, Johnson, Dwight, Kaplan, Edward, Lovgren, Marguerite, Reinert, Ralf Rene, Efstratiou, Androulla
• Format: Article
• Language: English
• Subjects: Antigens, Bacterial - analysis; Antigens, Bacterial - genetics; Bacterial Outer Membrane Proteins - analysis; Bacterial Outer Membrane Proteins - genetics; Bacterial Typing Techniques - standards; Bacteriological Techniques - standards; Bacteriology; Basic Medicine; Biological and medical sciences; Carrier Proteins - analysis; Carrier Proteins - genetics; Europe; Fundamental and applied biological sciences. Psychology; Genotype; Humans; Infectious diseases; Medical and Health Sciences; Medical sciences; Medicin och hälsovetenskap; Medicinska och farmaceutiska grundvetenskaper; Microbiology; Microbiology in the medical area; Mikrobiologi inom det medicinska området; Miscellaneous; Peptide Hydrolases - analysis; Quality Control; Sequence Analysis, DNA; Serotyping; Streptococcal Infections - microbiology; Streptococcus pyogenes; Streptococcus pyogenes - classification; Streptococcus pyogenes - isolation & purification
• ISSN: 0095-1137; 1098-660X; 1098-660X; 1098-5530
• DOI: 10.1128/JCM.02146-06

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.