Zebrafish intestinal colonization by three lactic acid bacteria isolated from Patagonian fish provides evidence for their possible application as candidate probiotic in aquaculture

Studies about probiotics isolated from Patagonian fish are scarce. Three autochthonous lactic acid bacteria (LAB) were previously isolated from Patagonian fish: Carnobacterium sp. T4, Lactococcus lactis TW34, and Lactobacillus pentosus H16. Zebrafish has been extensively used as an experimental vertebrate model; however, this model has recently been used to assess the intestinal bacterial colonization. In this study, we researched the in vitro probiotic properties of the Patagonian LABs T4, TW34, and H16, and their in vivo capability to colonize the gastrointestinal tract of zebrafish. Such strains were tolerant to trout bile and acid pH values, which is an essential property for their survival in the fish gut. H16 was the most resistant strain to low pH values. It specifically adhered to mucus, unlike T4 and TW34 that showed nonspecific adhesion. Zebrafish were fed daily with commercial food supplemented with T4, TW34, or H16 at a final concentration of 10 7 CFU g −1 of dry food, while the control group was fed only with commercial food. The presence of T4, TW34, and H16 was detected in the zebrafish intestines of the treated groups. After the treatments, changes in the zebrafish intestinal microbiota were recorded. The counts of vibrios and enterobacteria decreased, while the LAB count increased. This study showed that autochthonous LAB strains isolated from Patagonian fish were able to colonize the intestine of the zebrafish and modify the gut microbiota balance towards health-promoting bacteria. These findings propose them as interesting probiotic candidates for use in aquaculture purposes.