Innovative application of mass spectrometry for the characterization of staphylococcal enterotoxins involved in food poisoning outbreaks.

Staphylococcal poisoning is a common food-borne disease for which immunoassays to detect enterotoxins were developed, but these assays often lead to false diagnoses due to interferences or lack of specificity. Absolute quantitative mass spectrometry was for the first time successfully applied to an investigation of a staphylococcal outbreak due to coconut pearls.

Interlaboratory validation of the Vidas SET2 kit for detection of staphylococcal enterotoxins in milk products.

An earlier intralaboratory validation study based on the EN ISO 16140 Standard conducted by the Community Reference Laboratory for coagulase-positive staphylococci including Staphylocococcus aureus showed that, after an extraction step using dialysis concentration, the Vidas SET2 detection kit could be used to screen staphylococcal enterotoxins in milk and milk products. In order to fully validate Vidas SET2, an interlaboratory study was organized. Six freeze-dried samples and 3 ready-to-use concentrated extracts were analyzed by 21 laboratories according to the method, including a detection with Vidas SET2. Results did not show false-positive or -negative results. Accordance and concordance parameters were equal to 100%, corresponding to a concordance odds ratio of 1. This interlaboratory study confirmed the satisfactory outcome of the preliminary tests and of the intralaboratory study performed previously. The Vidas SET2 detection kit can be used as a method for the detection of staphylococcal enterotoxins in milk and milk products as well as the Transia Plate SET detection kit in the European screening method for official control purposes, after an extraction step followed by dialysis concentration.

How should staphylococcal food poisoning outbreaks be characterized?

Staphylococcal food poisoning is one of the most common food-borne diseases and results from the ingestion of staphylococcal enterotoxins (SEs) preformed in food by enterotoxigenic strains of Staphylococcus aureus. To date, more than 20 SEs have been described: SEA to SElV. All SEs have superantigenic activity whereas only a few have been proved to be emetic, representing a potential hazard for consumers. Characterization of staphylococcal food poisoning outbreaks (SFPOs) has considerably progressed compared to 80 years ago, when staphylococci were simply enumerated and only five enterotoxins were known for qualitative detection. Today, SFPOs can be characterized by a number of approaches, such as the identification of S. aureus biovars, PCR and RT-PCR methods to identify the se genes involved, immunodetection of specific SEs, and absolute quantification by mass spectrometry. An integrated gene-to-protein approach for characterizing staphylococcal food poisoning is advocated.