Identification and characterization of lactic acid bacteria isolated from rainbow trout (Oncorhynchus mykiss, Walbaum 1792), with inhibitory activity against Vagococcus salmoninarum and Lactococcus garvieae

In this study, a total of 98 lactic acid bacteria isolated from rainbow trout intestines were screened for their probiotic properties. The isolates were tested for their ability to inhibit growth of Vagococcus salmoninarum and Lactococcus garvieae. Based on in vitro antagonism, 10 isolates were selected and evaluated pathogenicity in rainbow trout. Isolates were further investigated for hydrophobicity, bile salts and acid tolerance. These isolates were able to survive low pH and high bile concentrations and showed good adherence characteristics. Isolates were characterized phenotypically, and then, 16S rRNA gene sequence analysis was used for confirmation. Selected strains were administered orally at 10(8)cfu/g feed, and fish were challenged with V. salmoninarum and L. garvieae. The fish fed with lactic acid bacteria supplemented diets did not improve protection against V. salmoninarum. However, administration of Lactococcus lactis subsp. lactis M17 2-2 and Lactobacillus sakei 2-3 resulted in a significant reduction in mortality due to L. garvieae when compared to the control fish. RPS values were calculated as 80 and 53% in fish fed with L. sakei 2-3 and L. lactis subsp. lactis M17 2-2, respectively. Our results suggest that these strains could provide an alternative for lactococcosis control in aquaculture.