title: High salinity relay as a postharvest processing strategy to reduce vibrio vulnificus levels in Chesapeake Bay oysters (Crassostrea virginica).
abstract: In 2009 the U.S. Food and Drug Administration (FDA) announced its intention to implement postharvest processing (PHP) methods to eliminate Vibrio vulnificus from oysters intended for the raw, half-shell market that are harvested from the Gulf of Mexico during warmer months. FDA-approved  PHP methods can be expensive and may be associated with unfavorable responses from some consumers. A relatively unexplored PHP method that uses relaying to high salinity waters could be an alternative strategy, considering that high salinities appear to negatively affect the survival of V.  vulnificus. During relay, however, oysters may be exposed to rapid and large salinity increases that could cause increased mortality. In this study, the effectiveness of high salinity relay to reduce V. vulnificus to <30 most probable number (MPN) per g and the impact on oyster  mortality were assessed in the lower Chesapeake Bay. Two relay experiments were performed during the summer and fall of 2010. Oysters collected from three grow-out sites, a low salinity site (14 to 15 practical salinity units [psu]) and two moderate salinity sites (22 to 25 psu), were relayed  directly to a high salinity site (≥30 psu) on Virginia's Eastern Shore. Oysters were assayed for V. vulnificus and Vibrio parahaemolyticus (another Vibrio species of concern) densities at time 0 prior to relay and after 7 and 14 days of relay, using the FDA MPN enrichment  method combined with detection by real-time PCR. After 14 days, both V. vulnificus and V. parahaemolyticus densities were ≤0.8 MPN/g, and decreases of 2 to 3 log in V. vulnificus densities were observed. Oyster mortalities were low (≤4%) even for oysters from the  low salinity harvest site, which experienced a salinity increase of approximately 15 psu. Results, although preliminary and requiring formal validation and economic analysis, suggest that high salinity relay could be an effective PHP method.
authors: Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, Virginia 23062, USA.
authors: Corinne
authors: C
authors: Audemard
authors: Howard I
authors: HI
authors: Kator
authors: Martha W
authors: MW
authors: Rhodes
authors: Thomas
authors: T
authors: Gallivan
authors: A J
authors: AJ
authors: Erskine
authors: A Thomas
authors: AT
authors: Leggett
authors: Kimberly S
authors: KS
authors: Reece
mesh_terms: D000818:Animals; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D005506:Food Contamination / Q000517:prevention & control; D005511:Food Handling / Q000379:methods*; D005519:Food Preservation / Q000379:methods*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010125:Ostreidae / Q000382:microbiology*; D012621:Seasons; D012758:Shellfish / Q000382:microbiology*; D012965:Sodium Chloride / Q000494:pharmacology*; D013997:Time Factors; D014736:Vibrio parahaemolyticus / Q000187:drug effects / Q000254:growth & development; D041261:Vibrio vulnificus / Q000187:drug effects / Q000254:growth & development*
chemical_list: D012965:Sodium Chloride