87-6 |
Comparison of Automated BAX system for Listeria monocytogenes with culture methods |
E. M. COLE1, G. Tice, and M. Barbour. (1) DuPont Qualicon, Bedford Building, 3531 Silverside Road, Wilmington, DE 19810 The automated BAX® for Screening family of PCR assays for foodborne pathogens (DuPont Qualicon) integrates DNA amplification and detection to determine the presence or absence of a specific target in a single instrument. All primers, polymerase, and deoxynucleotides necessary for PCR as well as a positive control and an intercalating dye are incorporated into a single tablet. This combination of simplified sample preparation and automated analysis makes the accuracy of genetics based screening more widely accessible to laboratories. The BAX® for Screening Listeria monocytogenes assay was compared to three reference methods to determine its utility. In order to determine maximum sensitivity limits, samples were inoculated so as to generate fractional positives. Three dairy products were tested against AOAC Method 993.12, eleven foods representing processed fish, meats and juices were compared to FDA-BAM, and deli turkey, dried powder egg yolks and ground pork were compared to the USDA/FSIS method. Seventeen foods were inoculated at high (11-50 cfu/25g), and low (1-10 cfu/25g) levels with 12 separate strains of L. monocytogenes. Each sample was processed using the recommended sample preparation procedure. Each inoculation level was replicated 20 times along with five uninoculated replicates. The PCR tablets were hydrated with lysates from the foods and processed on the automated detection instrument. The instrument conducted thermal cycling on the samples and then performed analysis to determine the presence or absence of L. monocytogenes. The overall method agreement was >98%. In this study of 680 inoculated samples, the automated PCR assay detected 72.3% and the reference methods 70.1%. These results are in line with the low inoculation levels. Performance on the uninoculated samples was also comparable. The automated PCR assay demonstrated superior sensitivity to the reference methods for the tested foods as well as providing a simple, easy to use implementation.
Session 87, Food Microbiology: General
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