IAFP 2009 Program Book and Abstract Book - AB74

Significance: This study is mainly intended to design a simple, easy and unbiased consumer guide for cooking shrimp to enhance safety of shrimp handled and cooked at home. It can also serve as a guide for manufacturers of Ready-to-Eat shrimp products in designing and planning GMPs and HACCP plans for production. P1-35 Effect of Gamma Irradiation on Inactivation of Foodborne Virus in Oyster JU-WOON LEE, Jae Seok Park, Beom-Seok Song, Jong-il Choi, Jae-Hun Kim, Yohan Yoon and Myung-Woo Byun Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Team for Radiation Food Science & Biotechnology, Jeongeup, Korea, South Introduction: Norovirus is well known as a pathogen in water and foods, but a study of norovirus in shellfish is complicated by a lack of enumeration methods for the virus. Purpose: Therefore, the objective of this study was to evaluate the inactivation effect of gamma irradiation on foodborne virus in oyster, using poliovirus as a surrogate for norovirus. Methods: In order to evaluate the antimicrobial effect of irradiation, 0.1 ml (6.5 log PFU/ml) of poliovirus (serotype poliovirus-1, ATCC VR-1562) was inoculated into 100 ml of phosphate buffered saline (PBS), and the samples were then gamma-irradiated at 0, 0.1, 0.2, 0.3, and 0.5 Gy. In addition, 40 oysters (Crassostrea gigas) within shells were placed in 7 L of artificial seawater (3% sea salt; wt/vol) contaminated with 4.9 log PFU/ml of poliovirus at 16°C in the dark for 2 h. Shells of oysters were then removed and the flesh submitted to gamma irradiation at 0, 0.5, 1, 2, 3, 4, and 5 kGy. Populations of the virus was enumerated by TCID50 (tissue culture infectious dose, log), and plaque forming unit (log) of poliovirus was further used to calculate D10 values by simple regression, and D12 values were also determined. Results: The number of poliovirus in PBS decreased (P < 0.05) by 2.7 log PFU/ml after irradiation, and the initial virus populations (5.4 log PFU/oyster) in oyster samples decreased (P < 0.05) significantly to 3.5 log PFU/oyster as irradiation dose increased. Moreover, D10 values in PBS and oysters were 0.46 kGy and 2.84 kGy, respectively, and D12 values were 5.52 kGy and 34.08 kGy for PBS and oyster, respectively. Significance: These results suggest that gamma irradiation may be useful in destroying foodborne virus in oysters, and food substrates may influence the antiviral effect of irradiation on foodborne viruses. P1-36 Norovirus Detection and Quantification in Shellfish Samples SOIZICK LE GUYADER, Sylvain Parnaudeau, Julien Schaeffer, Jean-Claude Le Saux and Robert L. Atmar Ifremer, Laboratoire de Microbiologie, Nantes, France Introduction: Noroviruses (NoVs) are the major agent responsible for nonbacterial gastroenteritis in humans and are present in large quantities in sewage during epidemic season. Shellfish concentrate NoVs in their digestive tissues when exposed to waters contaminated with sewage. As a consequence, NoVs are the most common cause of gastroenteritis outbreaks linked to shellfish consumption. Purpose: The finding that most NoVs are concentrated in digestive tissues led a decade ago to the development of a specific, reliable and reproducible method based on virus elution and concentration by PEG precipitation. Methods: Nucleic acid extraction and purification is accomplished with a kit based on magnetic silica, and viral RNA is detected in a one-step real time RT-PCR assay. By use of this method, six samples can be analyzed in one working day. An extraction control virus (Mengo virus) included in the assay, as well as internal controls, are employed as controls of virus and nucleic acid extraction and RT-PCR, respectively. Results: We evaluated the performance of this assay in bioaccumulated and naturally contaminated oysters. We observed good virus recovery and assay reproducibility for GI and GII NoVs and Mengo virus in bio-accumulated oysters. Triplicate extractions showed less than 0.5 log variations. Similar reproducibility was observed in the detection of GII NoVs in naturally contaminated oysters, but greater variability was seen for GI NoVs. The inclusion of control RNA and Mengo virus excluded the presence RT-PCR inhibitors as a possible explanation for the observed differences. Increased variability of the distribution of GI NoVs within oyster beds is a possible explanation for this result. This method was applied to estimate the level of NoV contamination in naturally contaminated shellfish (n = 100). The geometric mean concentrations of GI and GII NoVs, corrected for extraction efficiency, were 1,300 and 525 RNA copies/g of DT, respectively. This method was also applied to bioaccumulated oysters that were then subjected to cooking. Significance: In summary, this method for detection of NoV in shellfish is quite easy to perform and allows the analysis of several shellfish at one time. The rapidity of the assay may allow producers to evaluate their product prior to marketing. This quantitative approach also can be used for risk analysis, evaluation of virus persistence within the oyster, assessment of the impact of sewage in contaminated areas, and determination of the effectiveness of depuration. P1-37 Characterization of Salmonella spp. from Nopal Leaves and Associated Soil and Water Samples in Morelos, Mexico A. M. HERNANDEZ-A., P Landa-S., G. Mora-A., C. A. Eslava-C., J. E. Call, Anna C. Porto-Fett and J. B. Luchansky . Institution de Ensenanza e Investigacion en Ciencias Agricolas, Colegio de Postgraduados, Montecillo, Mexico Introduction: Introduction: Nopal is a native cactus species [Opuntia ficus-indica (L.) MILL (Cactaceae)] of great economic importance in Mexico. It is grown in open fields and subsequently ingested fresh as a salad or processed as a juice or yogurt, but it may also be used as a dietary supplement and/or for cosmetic products. Recent Salmonella outbreaks have resulted in renewed concerns about the incidence and control of this bacterium, particularly in fresh fruits and vegetables such as cantaloupe, tomatoes, bell peppers, and jalapeños. Purpose: The objective of this study was to determine the bacteriological safety of fresh cactus leaves (nopal) and the associated soil and water in Morelos, a cactus-producing region of south central Mexico. Poster 74 — Abstract Book

IAFP 2009 Program Book and Abstract Book

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