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SCREENING OF POTENTIAL PROBIOTIC BACTERIA FROM MARINE ENVIROMENTS ON THE COAST OF PATAGONIA FOR THEIR APPLICATION IN AQUACULTURE SYSTEMS
MELANIA FERNÁNDEZ; MARISA GARCÉS; CYNTHIA SEQUEIROS; NELDA LILA OLIVERA
Mar del Plata
Congreso; X Congreso Argentino de Microbiología General SAMIGE; 2014
Recently, aquaculture has become the fastest growing food-producing sector; therefore it has turned in an intensive activity where animals are exposed to high stress conditions. The abuse of antibiotics to control and/or prevent bacterial diseases has led to the apparition of antibiotic-resistant pathogens. The use of probiotics as sanitary prevention method improves the farmed fish quality and safety in aquaculture systems. The aim of this study was to assess in vitro probiotic characteristics of bacteria isolated from the Patagonian coast for their potential application in aquaculture. The strains isolated from sediments, algae and marine organisms were grown on TS and MRS whith NaCl (2% w/v) at 25ºC for 24-72h. To detect antimicrobial activity against fish pathogens the double layer method was performed. The culture supernatant of the strains showing antimicrobial activity was assessed by the agar-well diffusion assay. The following fish pathogens were used as indicator strains: Aeromona salmonicida, Yersinia ruckeri, Lactococcus garvieae, Carnobacterium piscicola, Listonella anguillarum, and Vibrio alginolyticus. Agar-cellophane assay was performed to remove the extracellular agent released by the strain M26 on solid medium. The cell adhesion ability was tested using the Crystal Violet assay. Siderophore production in the culture cell-free supernatants was evaluated by the agar CAS diffusion assay. Hemolysin and gelatinase production was determined as an indication of the microbiological safety of the selected strains. Eighty-two percent of the isolated strains showed inhibition against at least one of the indicator strains. Several strains isolated from gut of sea bass (Acanthistius patachonicus) and brazilian sand perch (Pinguipes brasilianus) showed a wide inhibition halo indicating that the antimicrobial agent diffused through the agar. None of the strains showed extracellular antimicrobial activity. The antimicrobial agent could not be removed by agar?cellophane assay. Strain 73 showed the highest adhesion ability to a hydrophilic surface. The strains evaluated by agar-CAS diffusion assay did not show siderophore production under the tested conditions. Two strains (T29 and T35) presented a slight haemolytic activity and only one (T39) showed gelatinase activity. Efforts to isolate and assess probiotic properties in native strains, such as those performed in this study, may lead to probiotic strains that could be used as biological control agents, reducing the antibiotic use and its negative environmental impact.