In conclusion, B. subtilis E20 is a potential pro-
biotic, which can be incorporated in the diet of
mud crabs for disease prevention through increas-
ing PO and phagocytic activities of haemocytes,
and disease resistance against V. parahaemolyticus
compared to crabs in the control, D7-40, and MD
groups. Antagonistic interactions among bacteria
must be considered prior to use of probiotics in
aquaculture as the health status of crabs fed the
MD diet did not improve due to the growth inhibi-
tion of B. subtilis E20 by L. plantarum 7-40. In
addition, the optimal concentration of B. subtilis
E20 in the diet for disease prevention in mud crabs
was determined to be