Preparation of Crassostrea gigas Samples Bioaccumulated by Vibrio vulnificus and Its Depuration Using UV-light

Abstract

Shellfishes mainly growing in coastal area are easily to be contaminated by various fecal matters such as in residential areas, livestock breeding grounds, wildlife habitats, and dock of vessel. As the results, shellfishes harvested in polluted shellfish growing area would contaminate various contaminates including pathogenic microbes and toxic chemicals such as heavy metals. In addition, especially oyster, often causes a severe vibrio infection such as vibrio sepsis due to the consumption of raw oyster contaminated by Vibrio vulnificus. V. vulnificus is a marine bacterium associated with foodborne illness and sepsis. This bacterium causes foodborne illnesses such as vomiting, diarrhea and abdominal pain when eating fish or shellfish contaminated with V. vulnificus. The object of this study is to evaluate the possibility of depuration of oyster contaminated by V. vulnificus that causes fatal sepsis. To progress this study, it firstly performed to prepare the suitable oyster samples. As a result, The oyster samples bioaccumulated by V. vulnificus with >8.0 log MPN/100g were used to evaluate the efficacy of depuration combined with UV irradiation. After 60 h of depuration, the cell number of V. vulnificus in oysters decreased by <3.52 log, that the reduction point of depuration efficiency suggested by NSSP guide line. In addition, no significant changes in pH and glycogen contents, an important factor of freshness and quality, were observed over the periods of depuration. These results strongly suggest that the depuration proposed in this study is very useful to purify oysters contaminated by V. vulnificus without losing freshness and quality.