Purpose: This study sought to identify changes in Vv, and total and pathogenic (tdh+/trh+) Vp levels in oysters during ambient storage (28-32°C) for 5 or 24h, then subjected to resubmersion (27-32°C) for two weeks.
Methods: Three 24h storage trials and two 5h storage trials were performed. For each trial, replicate oyster samples were collected at initial harvest (n=2), after ambient air storage (n=2), and after one (n = 4) and two (n = 4) weeks of resubmersion. Concurrently, oysters not ambient stored were collected as a background controls (n = 4). Bacteria levels were measured using an MPN enrichment followed by real-time PCR.
Results: After 5h oyster storage, the mean increase for both organisms was 1.2-1.3 log MPN/g. After 24h storage, the mean Vv and Vp levels increased by 1.5 and 2.3 log MPN/g, respectively. Pathogenic Vp levels increased <0.7 and 2.0 log MPN/g after 5h and 24h storage, respectively. Regardless of storage time, Vv and Vp levels returned to within 0.5 log MPN/g of background levels after one week of resubmersion. After two weeks of resubmersion, total Vv and Vp levels were within 0.1 and 0.4 log MPN/g of background levels, respectively. Pathogenic Vp levels in 24h stored oysters were within 0.5 log MPN/g after two weeks of resubmersion.
Significance: These data demonstrate that resubmersion of oysters exposed to elevated ambient temperatures allowed vibrio levels to return to background levels. These results can inform development of certain oyster aquaculture practices to minimize the risk of Vv and Vp illness.