Bacterial Isolated from <em>Oreochromis niloticus</em> and Possible Use as Probiotic

Abstract

The aim of this paper was to test isolated and pre-selected bacteria strains from Nile tilapia intestinal mucus, collected in Brazilian commercial fish farming, to use as probiotics in the feeding. The variable were growth performance, hematology, microbiology and immunology. These strains were submitted to in vitro inhibition tests of pathogenic bacteria. Then, they were identified by PCR and sequencing, and comparing using the BLAST software. The experiment was carried out in the Fisheries Institute, Sao Paulo, Brazil, for 84 days, following the randomized experiment design with seven treatments and three replicates (21 experimental units): T0 &amp;ndash; control, T1 &amp;ndash; Bacillus velezensis, T2 &amp;ndash; Bacillus pumilus, T3 &amp;ndash; Bacillus subtilis, T4 &amp;ndash;Enterococcus hirae T5 &amp;ndash; Enterococcus faecium and T6 &amp;ndash; mix of bacteria strains used to this experiment. The variables analyzed were: growth performance, DGGE (Denaturing gradient gel electrophoresis), phagocytes respiratory burst activity, hematology and bromatology. As result, the bacteria strains B. pumilus (T2) and all bacteria mix (T6), included in Nile tilapia diet, promoted better biomass values, with similar feed conversion rate of control group (p&amp;lt;0,05). Apparently, the microorganisms use does not affect the health and well-fare of the fish. The hematology index, except basophils and thrombocytes numbers do not demonstrated differences among the groups, as well as glycemia, lactate level, respiratory burst and lysozyme activities. In conclusion, the isolated and pre-selected bacteria from intestinal mucus of Nile tilapia, B. pumilus (T2) and mix (T6 - B. velezensis, B. pumilus, B. subtilis, E. hirae and E. faecium) improve the growth performance and may be used as probiotics for Nile tilapia.