IAFP 2009 Program Book and Abstract Book - AB105

P2-05 Evaluation of Three Methods to Recover Pathogens and Pathogen Surrogates from Whole Muscle Beef Jerky during Drying SARAH DIERSCHKE, Barbara Ingham and Steve Ingham University of Wisconsin, Food Science, Madison, WI, USA Introduction: The USDA/FSIS Microbiology Laboratory Guidebook for the Examination of Fresh, Refrigerated and Frozen Prepared Meat, Poultry and Pasteurized Egg Products instructs the user to prepare the sample for analysis by stomaching or blending for 2 min. Purpose: We investigated the recovery of pathogens (Escherichia coli O157:H7 and Salmonella spp.) and lactic acid bacteria (LAB) pathogen-surrogates (Biosource, Pediococcus acidilactici; and Saga 200, Pediococcus spp. ) from inoculated and marinated whole-muscle beef jerky strips manufactured in a small-scale commercial dehydrator or commercial smokehouse/oven. Methods: Samples in the dehydrator were dried at 68.3°C (155°F) for up to 8 h; samples in the Alkar oven were dried in a step-wise process: 54.5°C (130°F), 90 min; 60°C (140°F), 60 min; 65.6°C (150°F), 60 min; 70.1°C (160°F), 60 min; 76.7°C (170°F), 60 min. Processes were chosen because they reflect actual industry practice. Samples were taken post-inoculation, post-marination, and at intervals throughout the drying process. Surviving organisms were determined from meat strips homogenized using one of three methods: (1) stomaching for 2 min, (2) pulsifying for 2 min, or (3) dicing, soaking (5 min), then stomaching for 2 min. Results: Percentage Recovery of pathogens and LABs was calculated relative to post-inoculation or post-marination levels. For the 3 methods, 190, 156, and 190 samples, respectively, were analyzed. Based on post-inoculation levels, survival of LABs was significantly greater than survival of pathogens (P < 0.01) for each sampling time and each process, and there was significantly greater recovery of all organisms using homogenization method 3 (dicing/soaking/stomaching) across all conditions (2 processes, 2 marination formulations, 3 bacterial types), (P < 0.0001). Recovery with method 3 was enhanced by 0.42 logs for E. coli O157:H7, 0.61 logs for Salmonella spp., and 0.92 logs for both LABs. Significance: Care in preparation of meat samples, especially when the product undergoes case-hardening during processing, is important in evaluating the presence of pathogens and pathogen-surrogates in intermediate- or finishedproduct. P2-06 Evaluation of a Real-time PCR Assay for Detection of Listeria monocytogenes in Combination with New Sample Preparation and Data Analysis Software ROBERT S. TEBBS, Priya Balachandran, Lily Wong, Paolo Vatta, Maxim G. Brevnov, Manohar R. Furtado and Olga V. Petrauskene Applied Biosystems, Foster City, CA, USA Introduction: Listeria monocytogenes is a human pathogen that is ubiquitous in the environment and can be found in soil, wastewater, animals and vegetation. L. monocytogenes is robust and can survive extremes of temperature, pH, and salt concentrations. Detection of Listeria monocytogenes is of great importance to the food industry to protect their business and, more importantly, the health of their customers. We created a complete system for the detection of Listeria monocytogenes by real-time PCR that includes a lyophilized assay mix, sample preparation kits, instrumentation, and data analysis software. Purpose: To evaluate the systematic detection of Listeria monocytogenes that begins with sample preparation through data analysis. Methods: Food samples were spiked with and without 1 to 3 CFU Listeria monocytogenes and enriched according to standardized methods (25-g sample in 225-mL Buffered Listeria Enrichment Broth). Enriched samples were prepared for PCR using 2 sample preparation methods; PrepSEQ™ Rapid Spin Sample Preparation Kit, an PrepSEQ™ Nucleic Acids Detection Kit (both from Applied Biosystems). Real-time PCR was run on the Applied Biosystems 7500Fast instrument using a lyophilized TaqMan® assay mix, and analyzed using Rapid Finder Express software (Applied Biosystems). Results: The assay showed 100% detection of 50 Listeria monocytogenes isolates, and no detection of a panel of 30 non-Listeria monocytogenes strains. Early results on 4 food matrices spiked with 1 to 3 CFU showed that the Rapid Finder Express software correctly called 60/60 positive and 24/24 negative samples when samples were prepared with the PrepSEQ™ Rapid Spin Sample Preparation Kit. Significance: Real-Time PCR technology offers the benefits of rapid results, high sensitivity, and high specificity, as complete systems that include sample prep, software, and instrumentation simplify the workflow. P2-07 Evaluation of Idaho Technology’s R.A.P.I.D.® LT Listeria Food Security System in Select Foods and on Environmental Surfaces TRACI HAYES, Elijah Powell, Mike Powers, Jeffery J. Koziczkowski, Dorn L. Clark, Roy P Radcliff, Stephanie Thatcher . and Haleigh Millward Idaho Technology Inc., Research and Development, Salt Lake City, UT, USA Introduction: The Listeria LT Food Security System (FSS) is a PCR-based detection method that rapidly and specifically identifies Listeria species (monocytogenes, innocua, seeligeri, welshimeri, and ivanovii) in food and on environmental surfaces. Thermo-cycling takes only 30 min, and the entire procedure takes only 25-29 h. The method involves: a 24-28 hour sample enrichment, bacterial lysis to release DNA, DNA amplification by PCR in the Idaho Technology R.A.P.I.D. LT instrument, internal amplification controls, and automatic result interpretation by the software. Samples can be tested individually or pooled. Abstract Book — 105 Poster

IAFP 2009 Program Book and Abstract Book

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