The present study showed that the growth of pathogenic V.
harveyi was controlled by non-pathogenic B. subtilis BT23
under in vivo and in vitro conditions. The control of fish and
shellfish pathogenic Vibrio, particularly using non-pathogenic
bacterial strains and disease prevention, has received
much attention during the last decade (Sugita et al. 1998;
Rengipipat et al. 2000). Fuller (1989) defined a probiotic as a
live microbial feed supplement which benefits the host
animal by improving its intestinal microbial balance.
Co-culture experiments showed that the inhibitory activity
of B. subtilis BT23 increased with increasing density of the
antagonist.