Food Protection Trends - February 2010 - 89

Results: Average doses at the cantaloupe surface and at depths of 1 and 2 cm were 3.13 kGy, 2.27 kGy and 1.42 kGy, respectively. A stack of 6 allanine dosimeters immersed into the flesh showed max/min dose ratios from 1.19 to 1.61 kGy. Average log reduction of Salmonella Poona on cantaloupe after irradiation in the Maxim Chamber were > 4.7 and > 4.0 when inoculated on the rind and stem scar, respectively, and 4.7 and 3.9 when inoculated in the flesh at 1 and 2 cm under the surface, respectively. Conclusions: the Maxim Chamber seems to be an effective tool to uniformly deliver e-beam irradiation to products with spherical shapes. additionally, the advantage of reducing pathogen subcutaneously is highly remarkable due to current food safety concerns. Acknowledgments: We thank Dr. Mayra Marquez and Mr. Josue Morales for providing technical assistance. P1-05 Testing for Salmonella and Escherichia coli O157:H7 from a Single 8-h Enrichment Xuan Peng, Morgan Wallace, Dawn Fallon, Bridget andaloro, Lois Fleck, Lihong Wu, Dan Delduco and George Tice, DuPont Qualicon, R&D, Wilmington, DE 19880, United States Introduction: Introduction: Most Salmonella and E. coli o157:H7 outbreaks are linked to two food types: fresh produce and beef. traditional testing protocols call for separate enrichment methods when testing for Salmonella versus testing for E. coli o157:H7 in these matrices. Rational: Purpose: the objectives of this study were two-fold; one was to investigate using an established 8-h beef enrichment method with the BaX® system PCR method for detecting E. coli o157:H7 in fresh produce, and the other was to evaluate the same enrichment with the same PCR method for detecting Salmonella in both beef and produce. Methods: Produce was spiked with E. coli o157:H7, and beef and produce were spiked with Salmonella at target levels set to yield fractional positive results. samples were evaluated using the appropriate culture-based reference method and the PCR test kit method following the 8-h enrichment protocol. twenty spiked and five unspiked samples per food type per method were tested and compared. Results: statistical analysis on both E. coli o157:H7 and Salmonella in all matrices indicated the test method performed as well as or better than the reference method for detecting both E. coli o157:H7 and Salmonella. Conclusions: this approach demonstrated that both Salmonella and E. coli o157:H7 can be detected from the same 8-hour enrichment, which may save food companies cost, time and labor through reductions in sample preparation, media preparation, incubator space and waste streams. P1-06 Development of a Scorpion™ Probe-based Real-time PCR Assay for Genus Salmonella Daniel DeMarco and stephen Varkey, DuPont Qualicon, Wilmington, De 19880, United states Introduction: the use of PCR-based methods for Salmonella spp. detection and monitoring have shown tremendous growth in recent years. one commonly used commercial method, the BaX® system, uses end-point PCR based on melting curve analysis. although this method features excellent performance characteristics for sensitivity and specificity, it can require nearly 3.5 h to complete the cycling and melt curve analysis. Purpose: the purpose of this study was to evaluate the use of probe-based scorpion™ technology with existing primer sequences to develop a faster real-time PCR assay that would maintain performance identical or superior to the current end-point PCR assay. the use of probe detection allows for much more rapid cycling (< 1 h) and eliminated the need for a melt curve analysis. Methods: studies comparing the sensitivity and inclusivity of the new real-time assay with the current commercial PCR assay were conducted, using both purified Dna and select Salmonella spp. Results: Results using liquid real-time PCR reagents versus the tableted commercial PCR kit reagents showed equivalent sensitivity using both Dna (5 to 50 fg) and cells (~104 CFU/mL). Inclusivity using a small panel of 48 diverse Salmonella spp. was also identical with both assays, showing 100% detection of the strains tested. Significance: these results demonstrate the feasibility of developing a novel real-time PCR assay for Salmonella spp. that allows for cycling and detection in less than one hour, with the same performance characteristics of an existing well-characterized, commercial assay. P1-07 Validation of a PCR Assay for Screening Listeria spp. in Foods and Environmental Sponges Morgan Wallace, Bridget Andaloro, George Tice and Joanne Ruebl, DuPont Qualicon, Wilmington, DE 19880, United states Introduction: since other Listeria species can out-compete L. monocytogenes in culture, potentially leading to false negative results for the pathogenic species, some food producers are testing for Listeria spp. instead. Well-validated rapid methods for the detection of Listeria species as an indicator of possible product adulteration with L. monocytogenes are needed because culture-based take four to seven days to deliver a result. FEBRUARY 2010 | FOOD PROTECTION TRENDS

Food Protection Trends - February 2010

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