THE EFFECTS OF HANDLING TYPE ON THE LEVELS OF Vibrio vulnificus AND V. parahaemolyticus IN NORTH CAROLINA CULTURED OYSTERS

The routine handling of oysters is a common industry practice for off-bottom oyster farmers in order to produce a high-quality food product. These handling practices expose oysters to elevated temperatures, permissible for the growth of Vibrio parahaemolyticus (Vp) and V. vulnificus (Vv). Farmers can re-submerse their oysters in the water following routine handling, allowing the elevated levels of Vibrio to return to ambient levels before harvesting for raw consumption. In the past, our group has examined the effects of gear type, handling type, and season on re-submersion. However, these studies were only performed in two growing areas within Alabama waters, leaving open the question of geographic variation. With re-submersion being a relatively new topic in seafood safety, a similar study was performed on a farm in Cedar Island, North Carolina using floating cages in 2018-2019. In this study, the effects of two common types of handling (tumbling and refrigeration) were examined on Vibrio levels in oysters both initially and after re-submersion.  Both tumbling (tumbled, T; or not, NT) and refrigeration (refrigerated overnight, R; or not, NR) in four different experimental treatment combinations (TR, TNR, NTR, NTNR) were tested during a 24-hr removal from the water. Then, the recovery of levels of Vp and Vv levels during a 14-day re-submersion period was examined. A set of non-treated oysters that remained submerged throughout the study was tested to monitor ambient Vibrio levels over time. The preliminary data from 2018 suggest similar effects of the handling types on Vibrio levels as seen in a previous study in Portersville Bay, Alabama (2016-2017), with the non-refrigerated treatments experiencing significant increases in Vibrio levels. The data show that all Vibrio types recovered to ambient levels within the oysters after 7 days of re-submersion regardless of handling type, similar to the results of the Alabama studies. Final data from the four trials performed in 2018-2019 will be presented at the meeting.