Analysis of Staphylococcus enterotoxin B using differential isotopic tags and liquid chromatography quadrupole ion trap mass spectrometry

ABSTRACT Staphylococcus aureus produces enterotoxins, which are causative agents of foodborne intoxications. Enterotoxins are single‐chain polypeptides and have a molecular weight of about 26–28 kDa. The consumption of food contaminated with Staphylococcus aureus enterotoxins results in the onset of acute gastroenteritis within 2–6 h. The objective of this study was the development of a new method for the quantification of Staphylococcal enterotoxin B (SEB) in food matrices. Tryptic peptide map was generated and nine proteolytic fragments were clearly identified (sequence coverage of 35%). Among these, three specific tryptic peptides were selected to be used as surrogate peptides and internal standards for quantitative analysis using an isotopic tagging strategy along with analysis by LC‐MS/MS. The linearity of the measurement by LC‐MS/MS was evaluated by combining mixtures of both isotopes at 0.1, 0.2, 0.5, 1.0 and 2.0 1H/2H molar ratios with a slope near to 1, values of R2 above 0.98 and %CV obtained from six repeated measurement was below 8%. The precision and accuracy of the method were assessed using SEB spiked in chicken meat homogenate samples. SEB was fortified at 0.2, 1 and 2 pmol/g. The accuracy results indicated that the method can provide accuracy within a 84.9–91.1% range. Overall, the results presented in this manuscript show that proteomics‐based methods can be effectively used to detect, confirm and quantify SEB in food matrices. Copyright © 2011 John Wiley & Sons, Ltd.