Evaluation of a flow-through depuration system to eliminate the human pathogen Vibrio vulnificus from the eastern oyster (Crassostrea virginica)

Abstract

Evaluation of a flow-through depuration system to eliminate the human pathogen Vibrio vulnificus was carried out through altering 3 different parameters: salinity, temperature, and flow rate. Oysters were supplied by Auburn University Shellfish Laboratory (AUSL) and were from hatchery-reared stocks. Determination of V. vulnificus numbers in oyster tissues was conducted at 0, 1, 2, 3 and 6 days of depuration. Results showed that the numbers of V. vulnificus were significantly reduced by Day six in seven out of 14 trials. Also, only two out of 14 trials showed a significant difference between the test and control depuration systems. Laboratory-inoculated oysters were depurated from >100,000 CFU/g of V. vulnificus in oyster tissue down to 50 CFU/g in six days. Altered temperature and salinity parameters alone and together had very little success with reducing the numbers of V. vulnificus in oyster tissues. Flow rate increased to 68 L/m from 11 L/m resulted in a significant reduction of V. vulnificus in oysters in six days with an ending concentration of three CFU/g from a starting concentration of 110,000 CFU/g. Genotyping of the pre- and post-depuration isolates revealed no selection or resistance of by depuration of type A or B V. vulnificus. However, Amplified Fragment Length Polymorphism (AFLP) analysis did show that depuration does select some strains over others, reducing natural heterogeneity.