Zebrafish intestinal colonization by three lactic acid bacteria isolated from patagonian fish

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

San Miguel de Tucumán

Simposio; Simposio Internacional de Bacterias Lácticas; 2016

CERELA

Aquaculture, one of the fastest growingsectors of food production in the world, has suffered of serious losses due tobacterial diseases. The excessive use of antibiotics has led to the emergenceof resistant pathogens and antibiotic accumulation inside of fish tissues. Forthese reasons, probiotics are an interesting alternative for environmentallysustainable aquaculture. Many criteria must be satisfied to select probioticmicroorganisms. Among them, the ability to colonize the intestine of the hostis considered a critical feature. Currently zebrafish (Danio rerio) is used as a model to evaluate the efficiency ofprobiotics. 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 andTW34) using the zebrafish model. Assays were performed using one recirculatingsystem (three tanks) for each probiotic treatment (commercial feed inoculatedwith 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. Toassess changes in the intestinal microbiota, total viable bacteria, lactic acidbacteria (LAB), enterobacteria and vibrios were quantified by theplate-counting method at 2, 7 and 14 days during the probiotic treatment and 2days after the last probiotic administration. As the three probiotic strainshave antimicrobial activity against fish pathogens, their abundances were monitoredusing the double layer agar method. The results were expressed as CFU/g ofintestine. After 14 days of probiotic administration, the total viable countsof 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 withinprobiotic). In the same way, enterobacteria and vibrio counts declined inaverage one and a half order of magnitude, respectively; while LAB increasedapproximately two orders of magnitude in all three treated groups compared tothe control group. The ability of each strain to colonize the intestine wasdifferent. T4 and TW34 were recovered from the intestine only during theiradministration (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 recoveredfrom the intestine in a similar abundance to those registered in the administrationperiod (2.1x106 CFU/g). These results reveal that strains isolatedfrom the Patagonian fish could be used as probiotics to colonize the intestinaltract and modify the intestinal microbiota. Moreover, their different dynamicin the intestine gives insights into their administration as probiotics.