In Vitro Selection of Bacteria and Isolation of Probionts from Farmed Sparus aurata with Potential for Use as Probiotics

In the last years aquaculture has contributed significantly to reduce the hunger worldwide. One of the major treats in the development of a massive production is linked to the outbreak of diseases and the abuse of antibiotics, that is to avoid because of the acquisition of antibiotic resistance. For these reasons recently probiotics are used as alternative measures to control the fish diseases. Fish possess specific intestinal microbiota consisting of aerobic, facultative anaerobic and obligate anaerobic bacteria so we make this study in order to find some probiotic candidates that have an antagonistic action against fish pathogens. Adults of Sparus aurata farmed in intensive plant were sacrificed and 40 bacterial strains were isolated from GI tract. All the strains were tested against three fish pathogens: Vibrio anguillarum, Photobacterium damselae subsp. piscicida and Pseudomonas anguilliseptica. Results showed that only 3 candidates respectively called (SA7, SA10, and SA20) showed an inhibitory activity against the selected fish pathogens bacteria. The candidates probionts were identified by the 16S rRNA gene sequenced-based. The three candidates inhibited the Gram negative fish pathogens after 24 -48 h of incubation at 24°C and for these reasons could be used as probiotics to added into the food to enhance the immune defence of fish.