4 °C - the National Sea Grant Library

Survival rate of Y: vuZi2ifku.s in aouarium water
RESULTS AND DISCUSSION
The percent growth and survival of l? vuZnzjG~~ in aquariums rose by 15% to 36% during the 48
hours inoculation period and then began to drop(Fig. 1). The cell density of K vulnifcus in the
aquariums showed a slight increase during the initial inoculation period (2 days) and was then
followed by a decrease. Since the growth rate of V. vuZnzj&s during the inoculation period was
slow, the change of cell density was not significant.
Survival of V. vulnificus in heat treated ovsters
The results of the 50” C water heat treatment of inoculated shellstock oysters are presented in Table
1 and Table 2. The treatment was very effective in the reduction of K vuhificus in both 1.5 x lo5
MPN/g (high level) and 2.4 x lo3 MPN/g (low level). Time exposure of 5 min was sufficiently
effective to reduce the numbers of the pathogen by 99.9% Preliminary work on shucked oysters,
which lead to our study was reported by Cook and Ruple (1992). They reported death of
l?vuZnificus at temperature above 45OC and that 50° C was sufficient to reduce the bacterium to
undetectable levels.
Table 1. Effect of 50” C internal temperature heat treatment on the survival of V: vuZnzJ?cus in
the shellstock oysters treated with high level of contamination
Heating time J? vulnzj?cus MPN/g of oyster meat from high % Reduction
concentration level
0 min 1.5 x 10 5 0%
5mi.n
1omi.n