Discussion
Th e present study demonstrates the ability of
potential probiotic bacteria to control the pathogenic
Vibrio in in vitro and in vivo conditions. On diff usion
agar plates, B. coagulans and B. subtilis exhibited a zone
of clearance against pathogenic Vibrio. Th e inhibitory
mechanism of the interaction was not characterized
in this study. However, this result can be related
to the ability of Bacillus to produce antibacterial
compounds such as bacitracin, gramicidin S,
polymyxin, and tyrothricin, which are active against
a wide range of gram-positive and gram-negative
bacteria (16,17). A previous study suggested that
the inhibitory eff ects of Bacillus might be due to the
alteration of pH in the growth medium, utilization
of essential nutrients, or the production of volatile
compounds (18). Th e addition of potential probionts
to the Artemia culture enriched with commercial
food did not aff ect survival and showed a positive
eff ect on the development of the larvae. Similarly,
these strains enhanced protection against the target
pathogenic strain. Th ese results can be explained by
their great antagonistic ability to inhibit pathogenic
bacteria, possibly due to high doses that can induce
artifi cial and temporary dominance. Furthermore,
the ability of some microorganisms to adhere to
the intestinal tract and their eff ect in the digestive
processes of aquatic animals can participate in the
improvement of the Artemia culture and protection
against the pathogen (11). Th e positive eff ect of these
bacteria on the Artemia culture can be due to the
capacity of the bacteria to provide, either directly or
indirectly, nutritional elements like vitamins, fatty
acids, polyamines, and enzymes (19). Adhesion to an
abiotic surface partly explains the observed positive
eff ect of the tested strains during this study and
several others. In fact, this property can help Bacillus
strains to remain present in the bacterial fl ora of
the gut for several days, be active during intestinal
transit, participate in the digestion process, aid in
the elimination of potential pathogens, and create a
healthy environment (14). Several microbiological
studies have demonstrated the benefi cial eff ect of
Bacillus spp. on shrimp cultures. Balcazar and Luna-
Rojas (20) demonstrated that probiotics such as
Bacillus have potential applications for controlling
pathogenic Vibrio in shrimp aquaculture. Vaseeharan
and Ramasamy (4) found that growth of pathogenic