An immunomagnetic PCR signal amplification assay for sensitive detection of Staphylococcus aureus enterotoxins in foods. 2009

Leenalitha Panneerseelan, and Peter M Muriana
Department of Animal Science, Oklahoma State University, Stillwater, Oklahoma 74078-6055, USA.

Enterotoxigenic strains of Staphylococcus aureus produce a variety of heat-stable staphylococcal enterotoxins (SEs) that are a prevalent cause of food poisoning in the United States and other countries. Many immunological and biochemical assays often work well in buffer systems but are hindered when tested in the complex chemical environment of foods. To overcome these biases and improve the limits of detection, we implemented an immunomagnetic PCR signal amplification assay (iPCR-SA) for recovery and detection of SEA and SEB in foods. Anti-SEA or anti-SEB primary antibodies were coated onto COOH-modified magnetic beads using 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide reagent. Secondary antibodies were covalently linked to amino-modified reporter DNA oligonucleotides (563 bp) via the linker molecule succinimidyl-4[N-maleimidomethyl]-cyclohexane-1-carboxylate. An internal 159-bp portion of the reporter DNA retained by the captured toxin molecule was then amplified by real-time PCR. A semiautomated Bead Retriever proved extremely helpful in both the application of the conjugation chemistries and required washes and the recovery and washing of bead-conjugated toxin from tested food samples. The procedure was simple, and analyses were completed in 5 to 6 h. The assay was sufficiently robust that we were able to detect SEA and SEB in tryptic soy broth, milk, lemon cream pie, tuna salad, deli turkey, and ground turkey at levels as low as 7.5 fg/ml. SE was still detected at high sensitivity after heating in food samples for typical pasteurization or cooking regimens. Sensitivity was diminished only when samples were subjected to extreme heating.

UI MeSH Term Description Entries
D004768 Enterotoxins Substances that are toxic to the intestinal tract causing vomiting, diarrhea, etc.; most common enterotoxins are produced by bacteria. Staphylococcal Enterotoxin,Enterotoxin,Staphylococcal Enterotoxins,Enterotoxin, Staphylococcal,Enterotoxins, Staphylococcal
D004797 Enzyme-Linked Immunosorbent Assay An immunoassay utilizing an antibody labeled with an enzyme marker such as horseradish peroxidase. While either the enzyme or the antibody is bound to an immunosorbent substrate, they both retain their biologic activity; the change in enzyme activity as a result of the enzyme-antibody-antigen reaction is proportional to the concentration of the antigen and can be measured spectrophotometrically or with the naked eye. Many variations of the method have been developed. ELISA,Assay, Enzyme-Linked Immunosorbent,Assays, Enzyme-Linked Immunosorbent,Enzyme Linked Immunosorbent Assay,Enzyme-Linked Immunosorbent Assays,Immunosorbent Assay, Enzyme-Linked,Immunosorbent Assays, Enzyme-Linked
D005504 Food Analysis Measurement and evaluation of the components of substances to be taken as FOOD. Analysis, Food,Analyses, Food,Food Analyses
D005516 Food Microbiology The presence of bacteria, viruses, and fungi in food and food products. This term is not restricted to pathogenic organisms: the presence of various non-pathogenic bacteria and fungi in cheeses and wines, for example, is included in this concept. Microbiology, Food
D000906 Antibodies Immunoglobulin molecules having a specific amino acid sequence by virtue of which they interact only with the ANTIGEN (or a very similar shape) that induced their synthesis in cells of the lymphoid series (especially PLASMA CELLS).
D013211 Staphylococcus aureus Potentially pathogenic bacteria found in nasal membranes, skin, hair follicles, and perineum of warm-blooded animals. They may cause a wide range of infections and intoxications.
D016133 Polymerase Chain Reaction In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships. Anchored PCR,Inverse PCR,Nested PCR,PCR,Anchored Polymerase Chain Reaction,Inverse Polymerase Chain Reaction,Nested Polymerase Chain Reaction,PCR, Anchored,PCR, Inverse,PCR, Nested,Polymerase Chain Reactions,Reaction, Polymerase Chain,Reactions, Polymerase Chain
D018189 Immunomagnetic Separation A cell-separation technique where magnetizable microspheres or beads are first coated with monoclonal antibody, allowed to search and bind to target cells, and are then selectively removed when passed through a magnetic field. Among other applications, the technique is commonly used to remove tumor cells from the marrow (BONE MARROW PURGING) of patients who are to undergo autologous bone marrow transplantation. Immunomagnetic Bead Technique,Immunomagnetic Purging,Immunomagnetic Cell Separation,Bead Technique, Immunomagnetic,Bead Techniques, Immunomagnetic,Cell Separation, Immunomagnetic,Cell Separations, Immunomagnetic,Immunomagnetic Bead Techniques,Immunomagnetic Cell Separations,Immunomagnetic Purgings,Immunomagnetic Separations,Purging, Immunomagnetic,Purgings, Immunomagnetic,Separation, Immunomagnetic,Separation, Immunomagnetic Cell,Separations, Immunomagnetic,Separations, Immunomagnetic Cell

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