Refrigerated seawater depuration for reducing Vibrio parahaemolyticus contamination in Pacific oyster (Crassostrea gigas)
Seafood Research and Education Center, Oregon State University, Astoria, Oregon 97103, USA. Journal of food protection
(Impact Factor: 1.85).
The efficacy of refrigerated-seawater depuration for reducing Vibrio parahaemolyticus levels in Pacific oyster (Crassostrea gigas) was investigated. Raw Pacific oysters were inoculated with a mixed culture of five clinical strains of V. parahaemolyticus (10(5) to 10(6) most probable number [MPN] per g) and depurated with refrigerated seawater (5 degrees C) in a laboratory-scale recirculation system equipped with a 15-W gamma UV sterilizer. Depuration with refrigerated seawater for 96 h reduced V. parahaemolyticus populations by >3.0 log MPN/g in oysters harvested in the winter. However, 144 h of depuration at 5 degrees C was required to achieve a 3-log reduction in oysters harvested in the summer. Depuration with refrigerated seawater at 5 degrees C for up to 144 h caused no significant fatality in the Pacific oyster and could be applied as a postharvest treatment to reduce V. parahaemolyticus contamination in Pacific oysters. Further studies are needed to validate the efficacy of the depuration process for reducing naturally accumulated V. parahaemolyticus in oysters.
Available from: Thomas Alter
- "were still detectable, albeit at low concentrations. Barile et al. (2009), Wang et al. (2010), Ramos et al. (2012), and Su et al. (2010) observed the same trends for Vibrio parahaemolyticus. These bacteria remained in oysters for up to 2 wk. "
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ABSTRACT: Species of Vibrio can persist in blue mussels, especially when they are present in high numbers as a result of a large uptake from the aquatic environment. This study investigated the uptake, localization, and persistence of three Vibrio species relevant to human health in blue mussels (Mytilus edulis) after artificial contamination. Mussels M. edulis were kept in tanks of artificial seawater spiked with Vibrio spp. to monitor bioaccumulation of these bacteria in corresponding bivalves. Bacteria accumulated rapidly in the bivalves, reaching high concentrations after 1.5 h. The highest Vibrio sp. counts were detected in the digestive glands, with 6.9 × 108 cfu/g for Vibrio parahaemolyticus, 1.5 × 107 cfu/g for Vibrio cholerae, and 2.2 × 107 cfu/g for Vibrio vulnificus. Among bivalve compartments, the digestive glands showed the fastest enrichment of Vibrio and maintained the highest Vibrio numbers throughout the examination period. After transfer to a tank containing filtered, sterile seawater, the Vibrio load in bivalves showed a continuous reduction. However, even after 7 days of depuration, an average concentration of approximately 103 cfu/g remained in the digestive glands of M. edulis. In clearance assays, a general clearance rate of 0.02 log cfu/g/h was calculated for all three strains. For the first time, in vivo accumulation counts and clearance kinetics of Vibrio within mussel compartments are shown, highlighting a strong concentration of Vibrio in the digestive glands whereas other tissues continued to accumulate significantly less Vibrio.
Journal of Shellfish Research 12/2013; 32(3):855-859. DOI:10.2983/035.032.0329 · 0.79 Impact Factor
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ABSTRACT: Consumption of raw oysters has been linked to several outbreaks of Vibrio parahaemolyticus infection in the United States. This study investigated effects of ice storage and UV-sterilized seawater depuration at various temperatures on reducing V. parahaemolyticus in oysters. Raw Pacific oysters (Crassostrea gigas) were inoculated with a mixed culture of five clinical strains of V. parahaemolyticus (10290, 10292, 10293, BE 98-2029 and 027-1c1) at levels of 10⁴⁻⁶ MPN/g. Inoculated oysters were either stored in ice or depurated in recirculating artificial seawater at 2, 3, 7, 10, 12.5, and 15 °C for 4-6 days. Holding oysters in ice or depuration of oysters in recirculating seawater at 2 or 3 °C for 4 days did not result in significant reductions (P > 0.05) of V. parahaemolyticus in the oysters. However, depuration at temperatures between 7 and 15 °C reduced V. parahaemolyticus populations in oysters by >3.0 log MPN/g after 5 days with no loss of oysters. Depuration at refrigerated temperatures (7-15 °C) can be applied as a post-harvest treatment for reducing V. parahaemolyticus in Pacific oysters.
Food Microbiology 08/2012; 31(1):51-6. DOI:10.1016/j.fm.2012.02.004 · 3.33 Impact Factor
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ABSTRACT: This study investigated effects of water salinity (10, 20, 25 and 30 ppt), oyster types (diploid and triploid) and oyster sizes (extra small and medium) on depuration for reducing Vibrio parahaemolyticus contamination in Pacific oysters (Crassostrea gigas). Oysters were inoculated with a mixed culture of five clinical strains of V. parahaemolyticus to levels of 104−6 MPN/g and depurated in UV-irradiated water in a recirculating system at 12.5 °C for 5 days. Holding oysters (diploid, extra small) in water with a salinity of 10 ppt for 5 days resulted in about 2 log10 MPN/g reductions of V. parahaemolyticus, which were significantly smaller than those (>3.0 log10 MPN/g) observed in water with higher salinities (20–30 ppt). The types (diploid vs triploid) and sizes (extra small vs medium) of oysters appear to have no impact on the efficacy of depuration for reducing V. parahaemolyticus in oysters. However, the efficacy of depuration in reducing V. parahaemolyticus in oysters can be influenced by water salinity. Such a factor needs to be considered when developing a depuration process for eliminating V. parahaemolyticus in oysters.
Food Control 08/2013; 32(2):569–573. DOI:10.1016/j.foodcont.2013.01.025 · 2.81 Impact Factor
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