title: International quality assurance study for characterization of Streptococcus pyogenes.
abstract: 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.
authors.affiliation: Respiratory and Systemic Infection Laboratory, Health Protection Agency Centre for Infections, 61 Colindale Avenue, London NW9 5HT, United Kingdom. shona.neal@hpa.org.uk
authors.forename: Shona
authors.initials: S
authors.lastname: Neal
authors.forename: Bernard
authors.initials: B
authors.lastname: Beall
authors.forename: Kim
authors.initials: K
authors.lastname: Ekelund
authors.forename: Birgitta
authors.initials: B
authors.lastname: Henriques-Normark
authors.forename: Aftab
authors.initials: A
authors.lastname: Jasir
authors.forename: Dwight
authors.initials: D
authors.lastname: Johnson
authors.forename: Edward
authors.initials: E
authors.lastname: Kaplan
authors.forename: Marguerite
authors.initials: M
authors.lastname: Lovgren
authors.forename: Ralf Rene
authors.initials: RR
authors.lastname: Reinert
authors.forename: Androulla
authors.initials: A
authors.lastname: Efstratiou
mesh_terms: D000942:Antigens, Bacterial / Q000032:analysis / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis / Q000235:genetics; D015373:Bacterial Typing Techniques / Q000592:standards*; D001431:Bacteriological Techniques / Q000592:standards*; D002352:Carrier Proteins / Q000032:analysis / Q000235:genetics; D005060:Europe; D005838:Genotype; D006801:Humans; D010447:Peptide Hydrolases / Q000032:analysis; D011786:Quality Control; D017422:Sequence Analysis, DNA; D012703:Serotyping; D013290:Streptococcal Infections / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000145:classification* / Q000302:isolation & purification
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; C021908:opacity factor; C014689:streptococcal M protein; D010447:Peptide Hydrolases