Depuration of Oysters (Crassostrea gigas) Contaminated with Vibrio parahaemolyticus and Vibrio vulnificus with UV Light and Chlorinated Seawater

Abstract

The efficacy of depuration using UV light and chlorinated seawater for decontaminating Vibrio parahaemolyticus and Vibrio vulnificus from oysters was investigated. Oysters were contaminated with a five-strain cocktail of V. parahaemolyticus or V. vulnificus to levels of 10(4) to 10(5) CFU ml(-1) for bioaccumulation. The depuration was conducted in a closed system in which 350 liters of seawater was recirculated at a rate of 7 liters/min for 48 h at room temperature. Counts of V. parahaemolyticus or V. vulnificus were determined at 0, 6, 18, 24, and 48 h. Three treatments were conducted: T1, control treatment; T2, UV treatment; and T3, UV plus chlorine treatment. After 48 h of depuration of V. parahaemolyticus, T3 reduced the count by 3.1 log most probable number (MPN) g(-1) and T2 reduced the count by 2.4 log MPN g(-1), while T1 reduced the count by only 2.0 log MPN g(-1). After 48 h of depuration of V. vulnificus, T2 and T3 were efficient, reducing the counts by 2.5 and 2.4 log MPN g(-1), respectively, while T1 reduced the count by only 1.4 log MPN g(-1). The UV light plus chlorine treatment was more efficient for controlling V. parahaemolyticus in oysters. Both UV light and UV light plus chlorine were efficient for V. vulnificus. The present study is the first report showing the efficacy of depuration systems for decontaminating V. parahaemolyticus and V. vulnificus in oysters cultivated on the Brazilian coast. This study provides information on processes that can contribute to controlling and preventing such microorganisms in oysters and could be used for effective postharvest treatment by restaurants and small producers of oysters on the coast of Brazil.

Uptake and Localization of Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus in Blue Mussels (Mytilus edulis) of the Baltic Sea

“…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.…”

“…However, procedures combining depuration with other postharvest decontamination methods, such as applying high hydrostatic pressure or irradiation, are suitable (Jakabi et al 2003, Depaola et al 2009, Ramos et al 2012.…”

Depuration of Bacterial Populations in the Indian Backwater OysterCrassostrea madrasensis(Preston, 1916): Effects on Surface and Bottom Held Oysters

“…Most of the studies focused on testing depuration in different types of water (Vasconcelos & Lee 1972, Kasai et al 2011, Ramos et al 2012, and at different temperatures (Chae et al 2009, Love et al 2010, Lopez-Joven et al (Rowse & Fleet 1984, Power & Collins 1990, Love et al 2010, and densities (Lee 2010). However, there is little information on tropical oysters (Pillai & Selvan 1987) and no information on the effect of high-density stocking on depuration of tropical bivalves.…”

Factors Affecting the Uptake and Retention of Vibrio vulnificus in Oysters

“…Even though exogenous bacteria usually rapidly depurate around 72 to 96 h after introduction, the endogenous bacteria are notoriously resistant to depuration and using this technique has not been shown to increase the uptake of laboratory-grown bacteria (9,11,23,28,30). Allowing the oysters to bathe in high (Ͼ30‰)-salinity water before experimentation has proven successful in reducing the resident bacterial levels before beginning bioaccumulation experiments (8,17). Further information on the effects of water with elevated salinity on oyster V. vulnificus populations is presented below.…”

“…The "core" method is described first, followed by examples of deviation from this formula. The core method, elegant in its simplicity, is to grow the bacterial strain of interest to the desired concentration and seed an aquarium with a specific concentration of those bacteria, while allowing oysters within that aquarium to bioaccumulate the cells (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). The use of this method often yields similar results in which the bacteria are rapidly and significantly taken up by the oysters but quickly depurated to minimal or nondetectable levels within a few days (11,12,19,(22)(23)(24).…”