Characterization in vitro of new bacterial strains showing potentially probiotic crossed effect against vibriosis in relevant fish species for marine aquaculture

Intensive fish farms are often affected by different organisms that produce infectious diseases. To control this situation, antibiotics have been used with negative repercussions for the environment and health. As an alternative to this, probiotics are used that show more effective and respectful results with the environment. The aim of this project is to obtain new potentially probiotic strains against one of the most relevant pathogens of marine aquaculture, vibrios. These bacterial strains were isolated from the gills and intestines of European seabass, meagre and common sole. Later, were evaluated in vitro against 6 pathogenic strains of the genus Vibrio to demonstrate the production of antagonistic effects, production of antibacterial substances, resistance to bile, resistance to pH gradients, adhesion and growth to mucus, competition for nutrients and hydrophobicity. A total of 156 bacterial strains were isolated, but only 7 strains of the genera Alcaligenes, Pseudomonas, Shewanella and Proteus, showed excellent in vitro results to be considered as candidates to be reevaluated by in vivo tests, to determine their harmlessness and protective effect after challenge, and elucidating in future studies their use as possible probiotic strains for aquaculture, highlighting the results obtained with the strain Alcaligenes faecalis subsp. faecalis-1.