ZEBRAFISH INTESTINAL COLONIZATION BY THREE LACTIC ACID BACTERIA ISOLATED FROM PATAGONIAN FISH

MARISA GARCÉS; NELDA LILA OLIVERA; MELANIA FERNÁNDEZ; MARIANO MORIS; CECILIA CASTAÑOS; CYNTHIA SEQUEIROS

San Miguel de Tucumán

Simposio; SIBAL 2016 - V Simposio Internacional de Bacterias Lácticas.; 2016

Aquaculture, one of the fastest growing sectors of food production in the world, has suffered of serious losses due to bacterial diseases. The excessive use of antibiotics has led to the emergence of resistant pathogens and antibiotic accumulation inside of fish tissues. For these reasons, probiotics are an interesting alternative for environmentally sustainable aquaculture. Many criteria must be satisfied to select probiotic microorganisms. Among them, the ability to colonize the intestine of the host is considered a critical feature. Currently zebrafish (Danio rerio) is used as a model to evaluate the efficiency of probiotics. The aim of this study was to assess the in vivo survival dynamics and the effect on the intestinal microbiota of three Patagonian strains (T4, H16 and TW34) using the zebrafish model. Assays were performed using one recirculating system (three tanks) for each probiotic treatment (commercial feed inoculated with one probiotic strain (1x107 CFU/g)) and another system as a control (only commercial feed). Each of 12 tanks was randomly stocked with 30 fish. To assess changes in the intestinal microbiota, total viable bacteria, lactic acid bacteria (LAB), enterobacteria and vibrios were quantified by the plate-counting method at 2, 7 and 14 days during the probiotic treatment and 2 days after the last probiotic administration. As the three probiotic strains have antimicrobial activity against fish pathogens, their abundances were monitored using the double layer agar method. The results were expressed as CFU/g of intestine. After 14 days of probiotic administration, the total viable counts of bacteria significantly decreased in the treated groups (6.5x107, 3.4x107, and 5.2×106CFU/g for T4, TW34 and H16, respectively) compared to the control group (5.3×108 CFU/g within probiotic). In the same way, enterobacteria and vibrio counts declined in average one and a half order of magnitude, respectively; while LAB increased approximately two orders of magnitude in all three treated groups compared to the control group. The ability of each strain to colonize the intestine was different. T4 and TW34 were recovered from the intestine only during their administration (2.1x106 and 2.5x105 CFU/g for T4 and TW34 at 14 days, respectively). In contrast, 48h after the suspension of its administration, H16 was recovered from the intestine in a similar abundance to those registered in the administration period (2.1x106 CFU/g). These results reveal that strains isolated from the Patagonian fish could be used as probiotics to colonize the intestinal tract and modify the intestinal microbiota. Moreover, their different dynamic in the intestine gives insights into their administration as probiotics.