The use of phytogenic extracts is considered a sustainable strategy for the prevention of fish diseases, including Alliaceae as a potential option due to their variety of bioactive compounds.
In this study, we analysed the antibacterial potential of propyl-propane-thiosulfi nate (PTS) and propyl-propane-thiosulfonate (PTSO) from onions. The in vitro activity against Vibrio anguillarum , Tenacibaculum maritimum , and Photobacterium damselae subsp. piscicida of both compounds was tested by the determination of the Minimum Bactericidal Concentration (MBC) . In addition, a diet that consisted of a blend of PTS/PTSO in a proportion 1:1; w/w (300 mg/kg) was compared against to a control formula with no addition of PTS/PTSO; a total of 240 European seabass (Dicentrarchus labrax ) juveniles were challenged against V. anguillarum after 10 weeks of dietary administration.
All strains were sensitive to both compounds. PTSO showed the highest inhibitory effect against all target strains .
After the 10 weeks of dietary administration, f ish fed with PTS/PTSO included in the basal formula showed no differences in fish performance parameters (SGR, FCR and survival) compared to the control group. At termination of the V. anguillarum challenge, fish fed with PTS/PTSO included in the formula showed the highest survival, increasing up to 70.0 %, whereas in the control group, the survival was 51.2%. These results sugges t the inclusion of PTS and PTSO in feed as a natural strategy to prevent vibriosis in European sea bass.