Statistical analysis and quality control in radioimmunoassays for staphylococcal enterotoxins A, B, and C

Abstract

The objective of these studies was to set up a reliable radioimmunoassay (RIA) for staphylococcal enterotoxins A, B, and C (SEA, SEB, and SEC) in a food system. Significant differences (95% confidence limits) were obtained between the 0- and 1-ng/ml enterotoxin standards, so the sensitivity of the RIAs was 1 ng/ml. Polystyrene tubes coated with anti-SEB and stored at 4°C were unstable. The percentage of iodinated SEB bound to these tubes decreased at a rate of 0.33%/day, in contrast to the rate of 0.07%/day obtained with tubes prepared the day before the analyses. Satisfactory precision and maximum sensitivity were obtained by using 6 replicates for each sample and freshly coated tubes. The antisera used for coating the tubes were reused 4 times and were frozen between coatings. The process of drum drying mashed potatoes containing 1 μg of SEB per g of mashed potatoes inactivated 83% (wt/wt) of the SEB. Statistical quality control parameters were used to insure that RIAs were performing reliably with a sensitivity of 1 ng/ml. Over 450 samples of potato flakes and granules, which represented different production lots from 12 different manufacturers, were examined for SEA, SEB, and SEC. No enterotoxins were detected.