• Journal of fish pathology
• /
• v.27 no.2
• /
• pp.107-114
• /
• 2014

For the treatments and protection of bacterial fish disease, many requirements are needed for aquatic probiotics so that they are effective in aquaculture animals but are also harmless to humans. In the present study, among 17 candidate probiotic bacteria (CPB) obtained from the edible part of the shellfish, Bacillus sp. CPB-St (CPB-St) were selected and in vitro evaluated for the possibility as a probiotic strain for the control of fish streptococcosis which frequently occurs in the olive flounder farms. CPB-St showed inhibitory effects on the growth of various fish pathogenic bacteria, Streptococcus sp., S. parauberis, S. iniae, Lactococcus garvieae and L. piscium by the double layer test ranging about 18~26 mm of clear zone. Inhibitory activity of CPB-St to Streptococcus sp. was observed 6 hours after and the growth of Streptococcus sp. was decreased to 8~55 folds in the co-culture of CPB-St with Streptococcus sp.. The safety of CPB-St to fish and survival of CPB-St in the intestine were assessed in the olive flounder, Paralichthys olivaceus. Fish mortality was not observed in artificial infection with CPB-St for 2 weeks. CPB-St was entirely excreted from the stomach and intestine 24 hours after oral injection. This results indicate that CPB-St has potential applications as a probiotic for the control of fish streptococcosis in aquaculture.