Analysis of Staphylococcal Enterotoxin A in Milk by Matrix-Assisted Laser desorption/ionization-time of Flight Mass Spectrometry

Anal Bioanal Chem. 2011 May;400(5):1525-31. doi: 10.1007/s00216-011-4906-6. Epub 2011 Mar 27.


Staphylococcal enterotoxin A (SEA) is an exotoxin excreted mainly by Staphylococcus aureus and nowadays is the most prevalent compound in staphylococcal food poisoning worldwide. SEA is highly heat-resistant, and usual cooking times and temperatures are unlikely to completely inactivate it. A procedure for extraction of this toxin based on protein precipitation with a mixture of dichloromethane and acidified water was used before SDS-PAGE separation of soluble proteins. Finally, bands of interest were excised from the gel and in-gel enzymatic digestion was done. SEA from pasteurized milk was detected with matrix-assisted laser-desorption/ionization-time of flight (MALDI-TOF) mass spectrometry. Nineteen peptides (range 800-2400 Da) were identified as products of trypsin cleavage of the SEA standard with a score of 204 and 73% coverage of the protein sequence, whereas thirteen peptides were revealed for SEA extracted from milk with a score of 148 and 58% sequence coverage obtained. This procedure has been applied successfully for identification of SEA in milk.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cattle
  • Enterotoxins / chemistry
  • Enterotoxins / isolation & purification*
  • Milk / microbiology*
  • Molecular Sequence Data
  • Peptides / chemistry
  • Peptides / isolation & purification
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods*
  • Staphylococcus aureus / isolation & purification*


  • Enterotoxins
  • Peptides
  • enterotoxin A, Staphylococcal