Purpose: Within different harvesting regions there are naturally occurring dynamics and varying population levels of Vibrio parahaemolyticus (Vp) in oysters. The objective of this study is to investigate the reduction levels for Vp in oysters relayed within the seasonally changing Great Bay estuary of New Hampshire and Maine.
Methods: The effectiveness of the relocation (relay) of oysters from the Piscataqua River to Spinney Creek, a salt pond near Spinney Creek Shellfish Company (Eliot, ME), was assessed by sampling oysters on days 0, 7, 10, and 14. Vp concentrations in the oysters were determined using the 3-tube MPN enrichment method coupled to a cultured based confirmation assay in conjunction with genetic marker-based qPCR. Log concentrations of Vp were plotted against the relay sampling days for each month (June to September).
Results: Averaged concentrations of triplicate sample data for the four sampling days from day 0 to day 14 of the June, July, and August relays showed 1.08, 2.01, and 2.25 log reductions, respectively. A separate sample of oysters collected in August, that were temperature abused to increase initial Vp levels, showed a 4.5 log decrease from day 0 to 14.
Significance: Vp reduction in relayed oysters suggests the surrounding waters may have an effect on the extinguish of Vp from the oyster. Further investigation to discover the conditions that affect the Vp concentrations may aid in the treatment of oysters in the summer months prior to consumption.