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Validation and Verification Methods of Postharvest Processing Technologies Used to Eliminate the Human Pathogen Vibrio Vulnificus from Oysters


The main objective for this project is to set up a FDA-evaluated laboratory at Auburn University for PHP testing in oysters. <P>Specific objectives are: 1. To develop SOPs, QC and QA plans for detecting V. vulnificus in PHP-treated oysters 2. To validate new methodologies (ie, the recently AU-acquired DuPont Qualicon BAX System) with previously FDA-approved methods for the enumeration of this pathogen 3. To evaluate the efficacy of alternative non-lethal PHP techniques to reduce V. vulnificus levels in oysters 4. To assess abundance and persistence of V. vulnificus in farm-reared oysters

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Non-Technical Summary:<br/>
The eastern oyster is a key organism in coastal marine habitats where it acts as an ecosystem engineer by creating reefs as habitat for other marine species. In addition, oysters are economically important to consumers, seafood processors and retailers with an estimated 20 million Americans consuming raw oysters. The Gulf of Mexico accounts for 65% of the national total oyster production. However, oyster consumption has decline in the last few years due to public health safety concerns. Oysters are filter-feeders that concentrate bacteria present in their surrounding waters, including potential human pathogens such as Vibrio vulnificus. Currently, V. vulnificus infections are the leading cause for all seafood-related fatalities in the US, which are almost exclusively associated to the consumption of raw oysters. Overall, the incidence of vibrio infections has increased by 115% in the last 10 years according to the Center for Disease Control and the industry is under pressure to reduce the presence of these pathogens in oysters. Extensive studies have looked at distribution of vibrios in oysters and have identified key environmental factors (ie, water temperature and salinity) that have been used by FDA to develop current risk assessment models for V. vulnificus. It is expected that the FDA will move forward with a risk-based plan to regulate oyster consumption thus requiring PHP treatment of all oysters harvested during the warmer months. This will required all seafood processors to have their PHP methods validated/verified by FDA-evaluated laboratories. Currently, there are no FDA-evaluated laboratories in Alabama and the proposed project will ensure Auburn University will be the first institution in Alabama to host one of those labs.
Objective 1. SOPs, QA, and QC plans will be developed according to the National Shellfish Sanitation Conference and to the Bacteriological Analytical Manual edited by the Food and Drug Administration. Initially, Most Probable Number (MPN) followed by colony dot-blot confirmation will be used to enumerate V. vulnificus numbers. <br/>Objective 2. PCR-based protocols (ie., multiple BAX system) will be set up and validated against the MPN+colony dot-blot according to FDA guidelines. New PCR protocols should have the same sensitivity level (or higher) than the standard detection method. <br/>Objective 3. The potential of alternative PHP techniques such as depuration and relaying to uncontaminated waters to eliminate V. vulnificus from oysters will be evaluated using facilities at the Shellfish Laboratory in Dauphin Island. <br/>Objective 4. An incipient yet promising oyster aquaculture is being developed in Alabama. Growing conditions and oyster shellstock may influence numbers of V. vulnificus in farm-raised oysters. We will compare vibrio levels in oysters grown using different gear and different shellstocks (ie, diploids and triploids).
2012/01 TO 2012/12
<br/>OUTPUTS: 1. Development of Standard Operational Procedures (SOPs) and Quality Assurance/Quality Control (QA/QC) plans. A total of 45 SOPs have been written and assembled into a QA/QC plan that follows the National Shellfish Sanitation Conference and the Bacteriological Analytical Manual edited by the Food and Drug Administration. These SOPs and QA/QC plan have been implemented in our laboratory since last year. <br/>2. Oyster depuration. The use of high salinity depuration has been evaluated with adjusted feeding regimes and optimized temperatures to ensure not only the elimination of the pathogen Vibrio vulnificus but the preservation of maximum condition index in oysters.
<br/>PARTICIPANTS: Andrea Larsen, PhD candidate Stacey LaFrentz, Research Associate Cova Arias, Project Director.
<br/>TARGET AUDIENCES: Oyster industry FDA officials Seafood safety experts.
<br/>PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impact:<br/> 1. Our laboratory has been inspected by FDA and has been found to be in compliance with NSSF guidelines. Thus, we have become the only laboratory in Alabama approved for analysis of post-harvest treated oysters. <br/>2. Provided continuous service to the oysters industry from Lousiana, Mississippi, and Alabama. Regularly, analyzed post-harvest treated oysters.

Arias, Cova A
Auburn University
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