P2-181 Strategy for Quantification of Staphyloccous aureus Enterotoxins from Foodborne Intoxication Cases by Mass Spectrometry

Tuesday, July 11, 2017
Exhibit Hall (Tampa Convention Center)
Mirjana Andjelkovic , Scientific Institute of Public Health , Brussels , Belgium
Sarah Denaeyer , Scientific Institute of Public Health , Brussels , Belgium
Nadine Botteldoorn , Scientific Institute of Public Health , Brussels , Belgium
Andreja Rajkovic , Ghent University (UGent), Faculty of Bioscience Engineering, Department of Food Technology, Safety and Health, Research Unit Food Microbiology and Food Preservation (FMFP-UGent) , Ghent , Belgium
Introduction: Food poisoning caused by ingestion of Staphylococcus aureus enterotoxins (SET) is one of the most common foodborne-diseases and most of the SETs may induce symptoms by doses as low as 20-100ng per kg body weight. Since SET are thermostable, pH resistant and protease resistant proteins (20-30kD) they can withstand pasteurisation, food processing techniques and the acidic stomach environment.

Purpose: In the frame of microbial food safety risk assessment establishing the toxic dose easily measurable by using mass spectrometry prior to consumption is a big concern. This study provides specific and accurate analytical tools for detection and quantification of these toxins.

Methods: Whereas for A, B, C (C1, C2, C3), D and E serotype commercial kits are available other serotypes may only be indirectly concluded after PCR measurements.  For the purpose of the study six S.aureus H serotype producers from foodborne intoxications were identified and selected. With the extraction method recommended by the European Reference Laboratory for Coagulase positive Staphylococci, toxins were extracted from the S.aureus bacteria cultured on different growth media double Brain-Heart Infusion followed by the trypsin digestion of the extracted toxins (proteins) allowing the detection of its proteotypic peptides.

Results: Trypsin digests of enterotoxin (6 S.aureus isolates x 4 cell density x 3 growth phases x 3 replicates, including positive and negative control) were screened by liquid chromatography coupled to tandem mass spectrometry for the presence of the toxin using selected proteotypic heavy-labelled peptides as internal standards. The toxins were quantified in the extracts coming from the S.aureus isolates at the level of 4ng/g

Significance: LC-MS/MS approaches can be used for the detection and quantification of other SETs involved in foodborne outbreaks or clinical cases (eg asthma related extracts) and in risk assessment to determining the dose of SETs associated with toxicity.