Evaluation of Practical Post-Harvest Mitigation Strategies to Reduce the Abundance of Vibrio Bacteria in Molluscan Shellfish

Non-Technical Summary: Infections by Vibrio spp. increased by 41 percent from 1996-2005 and are at their highest levels since FoodNet began collecting data. These infections are most often associated with the consumption of raw seafood, particularly oysters. The U.S. Food and Drug Administration (FDA) recently announced its intent to require that oysters harvested during warm weather months receive a Post Harvest Process (PHP) to reduce levels of V. vulnificus (Vv). Since the announcement, the FDA has indicated that before implementation of this policy, it will work with stakeholders to identify and evaluate alternatives to existing PHP technologies. The proposed project will address this need by evaluating two potentially practical and cost effective post-harvest mitigation strategies. Study objectives include: 1) evaluate chill tank storage (CTS) and wet overboard storage (WOS) during the warmer months; 2) determine genetic profiles of natural Vv and Vibrio parahaemolyticus (Vp) isolated from CTS and WOS oysters; 3) use Smart ButtonsTM to monitor time temperature profiles of oysters during CTS and WOS; 4) estimate costs and benefits of the optimal CTS and WOS approaches; and 5) develop outreach and extension programs for control of Vv and Vp in postharvest oysters. This unique combination of multi-institutional research and outreach activities will help develop science-based control strategies. It will also heighten the research capacity in Food Science at the University of Maryland Eastern Shore. <P> Approach: Year 1 will focus on the use of chill water storage with UV, fluidized bed bio-filter, and protein skimmers with or without added hydrogen peroxide to reduce numbers of Vv and Vp in oysters. Analyses will include Vv and Vp and fecal coliforms and E. coli numbers in the oysters and Vibrio spp. and fecal coliform numbers in the chill tank water. Data will also be collected on the genetic profiles of Vv and Vp in post harvest oysters. In addition, preliminary studies will also focus on determining the effectiveness of overboard wet storage in high salinity waters (30-34 ppt) to reduce the numbers of Vv and Vp in oysters. Year 2 experiments will continue to focus on the effectiveness of overboard wet storage in high salinity waters (30-32 ppt) to reduce numbers of Vv and Vp in oysters. Temperature profile data will be collected on oysters during wet overboard storage with Smart ButtonsTM. Microbiological analyses will include Vv and Vp and fecal coliforms and E. coli numbers in the oysters. Data will also be collected on the genetic profiles of Vv and Vp in oysters using PFGE. Year 3 experiments will focus on determining economic costs of the optimum chill water tank and wet overboard storage of oysters. A validation study of the most promising mitigation strategies will also be conducted. Project results will be disseminated via classroom discussion, presentations at professional and industry meetings, and regulatory conferences. Workshops will be conducted to demonstrate the use of the practical post harvest mitigation strategies in reducing Vv and Vp in oysters. An evaluation committee comprised of investigators and collaborators of the project will meet at least twice annually to evaluate the progress of the projects and determine if any modifications are needed. In addition, the project director will regularly conduct meetings with the involved students and technician. Their needed skills and knowledge for the projects will be tested on a regular basis in order to maintain a consistent and competent level of research expertise. Samples will be promptly processed and data will be tightly scrutinized so that timely adjustments can be made to procedures, if needed.