| Abstrakt: |
Previous short-duration depuration studies with the eastern oyster (Crassostrea virginica) demonstrated difficulty in achieving significant naturally incurred Vibrio vulnificuspopulation count reductions. The present study used long-duration depuration (14 days) at controlled temperatures (10 or 22°C) and salinities (12, 16, or 20 mg/g). All depuration temperature–salinity combinations significantly reduced V. vulnificuscounts, with greatest reductions seen in 12 mg/g, 10°C seawater (2.7-log CFU/g reduction) and in 20 mg/g, 22°C seawater (2.8-log reduction). Mesophilic vibrios dominated the overall microflora of freshly harvested oysters, whereas refrigerated storage selected for psychrotrophic bacteria (Pseudomonasspp., Aeromonasspp., Shewanellaspp., Psychrobacterspp.) as well as did depuration at 10°C (Pseudoalteromonasspp., Shewanellaspp., Vibriospp.). Depuration at 22°C retained dominance of mesophilic vibrios, including pathogenic species, followed by Shewanellaspp., Pseudoalteromonasspp., and Photobacteriumspp. Although aerobic plate counts were lower in 22°C depurated oysters (5.0 log versus 6.0 log) compared with 10°C, depuration at 10°C offered greater V. vulnificuspopulation reductions than depuration at 22°C. This advantage was only seen at 12 mg/g salinity, with no impact at 16 and 20 mg/g salinities. No depuration treatment reduced V. vulnificuscounts to nondetectable levels. Use of prolonged depuration may be a helpful intervention to control V. vulnificuspopulations in oysters. |
