Recovery of Staphylococcal Enterotoxin in Multiple Phase Foods

Lipids are soluble in organic solvents and staphylococcal enterotoxins are water-soluble. This recognized feature can assist in the recovery of these toxins. Partitioning studies were conducted using a toxin-insoluble organic solvent (CHCl3) treatment for the extraction of toxins from the lipid portion of the tested food products. Enterotoxin serotypes A, B and D were added at toxin concentrations of 2ng/mL to five brands each of whole milk, 1% low fat milk, half and half, eggs, and two kinds of salad dressings. Pre-partition and post-partition extracts from the foods were assayed for toxin recovery using an enzyme-linked immunosorbent assay-based serological method. While the toxin was detected by traditional extraction procedures, toxin levels were retained in the precipitate of the food products. This study demonstrates that CHCl3 treatment in conjunction with concentrating the extract is beneficial when low levels of enterotoxin need to be identified. Practical ApplicationsTraditional extraction methods work well in most low-fat containing foods; however, multiple CHCl3 extractions are advantageous when testing high-lipid containing foods or foods that may contain small traces of enterotoxin. This method proved valuable when extracting small quantities of staphylococcal enterotoxin from the lipid fraction of foods.