Département Médicaments et Technologies pour la Santé (DMTS), SPI, Université Paris-Saclay, CEA, INRAE, 91191 Gif-sur-Yvette, France.
Laboratory for Food Safety, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), Université Paris-Est, 94700 Maisons-Alfort, France.
J Agric Food Chem. 2021 Mar 3;69(8):2603-2610. doi: 10.1021/acs.jafc.0c07545. Epub 2021 Feb 17.
Staphylococcal enterotoxins (SEs) are responsible for frequent food poisoning outbreaks worldwide. Specific identification of SEs is crucial for confirmation of food poisoning, tracking of the incriminated foods or food ingredients, and removal from the food chain. Here, we report on a new food testing protocol addressing the challenge of low abundance of SEs in contaminated food and high sequence heterogeneity. Multiplex ability of targeted high-resolution mass spectrometry was succesfully applied to the simultaneous and quantitative determination of the eight most frequent SEs including sequence variants. In this aim, between three and eight proteotypic peptides of each SE were selected by carefully considering amino acid variations within each type, and sequence homology between types. Quantification of trace levels of SEs directly in food samples was reached by immunoaffinity enrichment and optimized analytical conditions. The assay was validated in dairy food products with a lower limit of quantification down to 0.1 ng/g (in milk), and quantification of SEs was successfully demonstrated in real-life samples collected during staphylococcal food poisoning outbreaks. Importantly, the ability of the method to detect diverse sequence variants was also illustrated. By enabling for the first time the simultaneous quantification of the eight most frequent SEs, the new mass spectrometry-based assay would facilitate the laboratory confirmation of positive samples in situation of food poisoning outbreaks.
葡萄球菌肠毒素（SEs）是导致全球频繁发生食物中毒的罪魁祸首。对 SEs 的特异性鉴定对于确认食物中毒、追踪罪魁祸首的食物或食物成分以及从食物链中去除至关重要。在这里，我们报告了一种新的食品检测方案，该方案解决了污染食品中 SEs 含量低和序列高度异质的挑战。靶向高分辨率质谱的多重能力成功应用于同时定量测定包括序列变异体在内的八种最常见的 SE。为此，通过仔细考虑每种类型内的氨基酸变异和类型之间的序列同源性，选择了每种 SE 的 3 到 8 个特征肽。通过免疫亲和富集和优化的分析条件，直接在食品样品中痕量水平的 SE 进行定量。该测定方法在乳制品中进行了验证，定量下限低至 0.1ng/g（在牛奶中），并成功证明了在食源性葡萄球菌食物中毒暴发期间采集的实际样本中 SE 的定量。重要的是，该方法检测多种序列变异体的能力也得到了证明。通过首次能够同时定量测定八种最常见的 SE，新的基于质谱的检测方法将有助于在食物中毒暴发时对阳性样本进行实验室确认。
