4 °C - the National Sea Grant Library

4. Differentiate V. parahaemolyticus and V. vulnificus by halophilism
and ONPG tests.
5. Repeat the same procedures after 7 and 14 days, respectively.
Results and Discussions
V. parahaemolyticus is very sensitive to gamma irradiation. The
D value is only 0.05 kGy. They were totally eliminated by 0.5 kGy of
gamma irradiation. The results of gamma irradiation on V.
parahaemolyticus counts are shown in Table 2
Table 2. The effect of gamma irradiation and 2°C ice storage on
V. parahaemolyticus
Day Control 0.125 0.25 0.5 0.75 1.0 1.5 2
kGy kGy kGy kGy kGy kGy kGy
0 4.88 3.8 NC 0 0 0 0 0
7 4.32 3.4 NC NC 0 0 0 0
14 4.18 NC NC NC 0 0 0 0
The numbers are expressed in Log 10 CFU/g ; NC: Not Countable, the
number of CFU from the maximum dilution < 25 in one plate.
The D value and effect of ice storage on survival numbers of V.
parahaemolyticus are shown in Figure 3. and Figure 4.
The numbers of V. parahaemolyticus kept decreasing during ice
storage, indicating that low temperature (2°C) is inhibitory to this
organisms.
Listeria monocytogenes
McBride Listeria medium was employed to detect and enumerate
Listeria monocytogenes.