title: Certified reference materials for testing of the presence/absence of Staphylococcus aureus enterotoxin A (SEA) in cheese.
abstract: Staphylococcal enterotoxins (SEs) account for a substantial number of food-poisoning outbreaks. European legislation (Commission Regulation 1441/2007) stipulates the reference procedure for SE analysis in milk and dairy products, which is based on extraction, dialysis concentration and immunochemical detection using one of two approved assays (VIDAS(®) SET2, Ridascreen(®) SET Total). However, certified reference materials (CRMs) are lacking to support laboratories in performing reliable detection of Staphylococcus aureus enterotoxin A (SEA) in relevant matrices at sub-nanogram per gram levels. The certification of a set of three reference materials (blank and two SEA-containing materials) for testing of the presence/absence of SEA in cheese is described. The reference procedure was applied in an intercomparison with 15 laboratories, and results were reported in a qualitative manner (presence or absence of SEA in the sample). No false-negative or false-positive results were obtained. The certified values were stated as diagnostic specificity (blank material) or diagnostic sensitivity (SEA-containing materials) and were 100 % in all cases. Stability studies demonstrated suitable material stability when stored cooled or frozen. An in-house study on the recovery of SEA in the cheese materials using a double-sandwich enzyme-linked immunosorbent assay (ELISA) revealed comparable recovery values of around 45 % at the two spiking levels and in both the SEA-containing CRMs as well as blank CRM freshly spiked prior to analysis. The values were also comparable over time and among different analysts. The materials provide valuable support to laboratories for method validation and method performance verification and will increase the reliability of measuring SEA in cheese.
authors.affiliation: European Commission, Joint Research Centre, Institute for Reference Materials and Measurements (IRMM), Retieseweg 111, 2440, Geel, Belgium. reinhard.zeleny@ec.europa.eu.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Zeleny
authors.affiliation: Laboratory for Food Safety, Université Paris-Est, ANSES, 94700, Maisons-Alfort, France.
authors.forename: Yacine
authors.initials: Y
authors.lastname: Nia
authors.affiliation: European Commission, Joint Research Centre, Institute for Reference Materials and Measurements (IRMM), Retieseweg 111, 2440, Geel, Belgium.
authors.forename: Heinz
authors.initials: H
authors.lastname: Schimmel
authors.affiliation: Laboratory for Food Safety, Université Paris-Est, ANSES, 94700, Maisons-Alfort, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Mutel
authors.affiliation: Laboratory for Food Safety, Université Paris-Est, ANSES, 94700, Maisons-Alfort, France.
authors.forename: Jacques-Antoine
authors.initials: JA
authors.lastname: Hennekinne
authors.affiliation: European Commission, Joint Research Centre, Institute for Reference Materials and Measurements (IRMM), Retieseweg 111, 2440, Geel, Belgium.
authors.forename: Håkan
authors.initials: H
authors.lastname: Emteborg
authors.affiliation: European Commission, Joint Research Centre, Institute for Reference Materials and Measurements (IRMM), Retieseweg 111, 2440, Geel, Belgium.
authors.forename: Jean
authors.initials: J
authors.lastname: Charoud-Got
authors.affiliation: Laboratory for Food Safety, Université Paris-Est, ANSES, 94700, Maisons-Alfort, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Auvray
mesh_terms: D002568:Certification; D002611:Cheese / Q000382:microbiology*; D004768:Enterotoxins / Q000032:analysis* / Q000592:standards*; D005060:Europe; D005504:Food Analysis / Q000592:standards*; D005506:Food Contamination / Q000032:analysis*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013211:Staphylococcus aureus / Q000378:metabolism*
chemical_list: D004768:Enterotoxins; C026066:enterotoxin A, Staphylococcal
keywords: Certified reference material; Presence/absence testing; Recovery study; SEA; Staphylococcal enterotoxins