Evaluation of a flow-through depuration system to eliminate the human pathogen vibrio vulnifcus from oysters

Abstract

The effcacy of a fow-through depuration system in eliminating the human pathogen Vibrio vulnifcus from eastern oysters (Crassostrea virginica) collected from the North Gulf of Mexico coast was evaluated in this study. Depuration experiments were conducted with artifcially inoculated oysters using laboratory-grown strains of V. vulnifcus as well as with naturally contaminated oysters. Determination of V. vulnifcus numbers in oyster tissues was conducted at 0, 1, 2, 3 and 6 days of depuration. Results showed that the depuration of V vulnifcus is possible using a fow-through system. Numbers of V. vulnifcus in laboratory-inoculated oysters were reduced from >100,000 Most Probable Number (MPN)/g of oyster tissue to 23 MPN/g after six days of depuration. As expected depuration results of naturally contaminated oysters were more variable. Depuration at low temperature (15°C) had very little success in reducing the numbers of V. vulnifcus in oyster tissues. On the contrary, when fow rate was increased from 11 L/m to 68 L/m, numbers of V. vulnifcus in oysters were reduced from a starting concentration of 110,000 MPN/g to 3 MPN/g in six days. Nevertheless, a high-fow rate was not enough to eliminate V. vulnifcus from oysters consistently. Vibrio vulnifcus was effectively eliminated from oysters only when incoming water salinity was higher than 30 parts per thousand (ppt). Depuration did not select for pathogenic V. vulnifcus strains. Pre- and post depuration V. vulnifcus isolates contained similar proportions of the proposed more virulent type. © 2010 Lewis M, et al.