Submitted to: Journal of Rapid Methods and Automation in Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/22/2003
Publication Date: 11/22/2003
Citation: MEDINA, M.B. DETECTION OF STAPHYLOCOCCAL ENTEROTOXIN B (SEB) WITH SURFACE PLASMON RESONANCE BIOSENSOR. JOURNAL OF RAPID METHODS AND AUTOMATION IN MICROBIOLOGY. p. 225-243. 2003. Interpretive Summary: The food industry needs routine methods to detect trace levels of bacterial enterotoxins produced by Staphylococcus aureus. This bacteria produces toxins that cause a major foodborne gastroenteritis, and trace amounts can cause symptoms of food intoxication. Under temperature abused conditions, the bacteria can grow in foods of animal origin and can also be transmitted by humans through unsanitary practices or through infected cuts or wounds. Heat processing and normal cooking temperatures kill the bacterial cells but the enterotoxins are not destroyed, thus illness can still occur. We developed a rapid and semi-automated method to detect a highly heat resistant toxin, SEB (staphylococcal enterotoxin B) using a biosensor. The biosensor method can capture the SEB in food samples and determine how much SEB is present. In experiments of SEB added to ham extracts and ham surfaces, trace amounts were detected as low as 2.5 parts per billion. This technique has advantages over previously reported biosensor methods, and it has the potential for simultaneous detection of several bacterial toxins in a single food sample. Using this approach, the safety of processed foods can be assured by testing for trace amounts of the toxins.
Technical Abstract: An automated and rapid method for detection of staphylococcal enterotoxins is needed by the food industry. We have developed a biosensor "Sandwich Assay" using a surface plasmon resonance (SPR) biosensor for the detection of Staphylococcus aureus enterotoxin B (SEB). The assay is based on the immobilization of SEB antibody, capturing the SEB from the standard solutions or samples, and followed by the capture of the second SEB antibody by the sensor surface. The assay conditions were optimized to detect SEB in Hepes buffer and in ham extracts. The results indicated that SEB can be detected at 2.5 ng/ml of HBST buffer or in ham tissue extract. The calibration lines of 8 replicate analyses were determined from SEB spiked in ham extract and resulted in a mean residue squared of 0.982 (SD=0.026) and 0.995 (SD=0.005) from SEB spiked in the supernatant of the centrifuged ham extract. Analysis of 10 and 20 ppb SEB inoculated on the surface of ham slices resulted in recoveries of 78+/-8%, and 74+/-12%, respectively. At lower doses of 2.5 and 5 ppb SEB, the recoveries were poor. The extraction procedure can be improved to increase recoveries and the utilization of a more specific antibody can also improve the detection sensitivity. The Biacore method of analysis is semi-automated and can be developed for multi-toxin detection in food.