Flow rate of depuration system has minimal impact on Vibrio parahaemolyticus decontamination in Pacific oysters (Crassostrea gigas)

Abstract

Vibrio parahaemolyticus infections in the United States have been linked to consumption of raw oysters. Depuration has the potential to reduce contamination in live oysters after harvest. This study investigated the impact of depuration flow rate to reduce V. parahaemolyticus in raw oysters. Pacific oysters (n = 35 per trial) were inoculated with a cocktail of V. parahaemolyticus (10290, 10292, 10293, BE 98‐2029, and 027‐1c1) in freshly prepared artificial seawater (70 L). The inoculated oysters were depurated with flow rates of 15, 20, 25, and 35 L/min at 12.5 °C for up to 5 days and V. parahaemolyticus contamination was determined using a three‐tube most probable number (MPN) method. V. parahaemolyticus reductions were as flow rate moderately increased from 15 L/min (2.39 log MPN/g reduction in 5 days) to 35 L/min (3.39 log MPN/g reduction). These results suggest that depuration efficacy can be enhanced by increasing depuration flow rate to 35 L/min. Practical applications Vibrio parahaemolyticus can contaminate raw shellfish, including oysters, during their production and lead to outbreaks of foodborne illness. Depuration, a post‐harvest process, may be used by the shellfish industry to reduce the persistence of V. parahaemolyticus. Previous studies have demonstrated that the depuration process can reduce V. parahaemolyticus in oysters; however, further optimization of the process is necessary to achieve US Food Drug Administration's targeted reduction goal (>3.52 log MPN/g). This study evaluated the impact of depuration flow rate on the reduction of V. parahaemolyticus in Pacific oysters. Increasing flow rates (15–35 L/min) during depuration enhanced the clearance of V. parahaemolyticus in these oysters; however, these conditions were unable to consistently achieve the target of >3.52 log MPN/g reduction. This study provides a reference for the industry on the variability of V. parahaemolyticus in individual oysters and demonstrates that practical modifications (i.e., flow rate) can be implemented in depuration systems to maximize bacterial clearance.

Depuration of live oysters to reduce Vibrio parahaemolyticus and Vibrio vulnificus: A review of ecology and processing parameters

“…Reductions in VV and VP were lower (<3 log MPN/g) when processing took place over 1–3 days compared with longer processing times (Chae et al., 2009). Other studies demonstrated higher reductions of VV and VP (≥3 log MPN/g) in oysters when depuration time was more than 3 days (Ming et al., 2018a; Phuvasate et al., 2012; Phuvasate & Su, 2013; Su et al., 2010; Wang, Yu, et al., 2010).…”

“…Another study examined flow rates from 15 to 35 L/min and confirmed higher flow rate might enhance depuration in oysters; however, the authors did confirm that depuration time had a more significant impact in the reduction of VP in Pacific oysters than flow rates (Ming et al., 2018a). The authors also noted depuration flow rate may contribute to modulating an oyster's pumping activity.…”

Depuration processes affect the Vibrio community in the microbiota of the Manila clam, Ruditapes philippinarum

“…For this purpose, several studies have conducted an artificial contamination of shellfish product with human pathogenic Vibrio species. The efficiency of the treatment is evaluated in terms of duration of the depuration cycle, water flow rate and density of shellfish per tank to remove the contamination of Vibrio pathogenic species (Barile et al ., 2018; Ming et al ., 2018; Shen et al ., 2019). Other studies investigated the impact of depuration on shellfish products naturally contaminated by Vibrios mainly describing the presence of human pathogenic Vibrio species such as V. cholerae 01, V. parahaemolyticus and V. vulnificus (Croci et al ., 2002; Sferlazzo et al ., 2018; Tokarskyy et al ., 2019).…”