This study aimed to isolate native lactic acid bacteria of yellow tail lambari (Astyanax bimaculatus) and evaluate their effect on host microbiota and gut morphology, as well as survival after experimental challenge. The isolated bacterial strains were evaluated for their inhibition against pathogenic bacterial strains in vitro, and the strain with highest inhibitory ability was molecularly identified as Lactobacillus spp. For in vivo testing, eighty fish were distributed in ten tanks equipped with a recirculation system. The experimental units were divided into two treatments: fish fed with Lactobacillus spp. supplement and fish fed an unsupplemented diet (control). After 30 days, guts from three fish from each experimental unit were pooled for microbiological and histological analysis. The other five fish were inoculated with 2.1x104CFU.mL-1 of Aeromonas hydrophila to evaluate survival after 24h. Lambaris fed with the probiotic diet had a lower count of Vibrios spp., Pseudomonas spp. and Staphylococcus spp., and a higher count of lactic acid bacteria compared to control treatment, as well as, increased length, width and perimeter of intestinal villi, as well as higher survival rate (16.2%) after experimental challenge compared to the unsupplemented group. The results show that the Lactobacillus spp. used has effect probiotic for yellow tail lambari.
Lactobacillus; yellow tail lambari; gut morphology; microbiota; experimental challenge