In vitro assessment of potential probiotic characteristics of indigenous Lactococcus lactis and Weissella oryzae isolates from rainbow trout (Oncorhynchus mykiss Walbaum)

Aim The objective of this study was to evaluate the probiotic potential of lactic acid bacteria (LAB) isolated from the intestinal ecosystem of rainbow trout. Methods and Results Among LAB isolates, 10 of them were selected and screened for resistance to acid and bile salts, pancreatin, sodium chloride and temperature, hydrophobicity, growth profile and antimicrobial activity against fish pathogens. Then, biosafety assessments were investigated. Selected LAB tolerated to gastrointestinal physiological conditions, pancreatin and a range of sodium chloride and temperature. They also exhibited hydrophobicity and showed antagonistic activity against Streptococcus iniae and Yersinia ruckeri. Results of 16S rRNA gene sequencing showed that selected LAB belonged to the Lactococcus lactis (n = 5) and Weissella oryzae (n = 5) species. They exhibited no β‐haemolytic activity, while six selected LAB were resistant to some antibiotics. None of them harboured virulence factors. Conclusions This study revealed probiotic characteristics of indigenous LAB isolated from the intestinal ecosystem of rainbow trout. However, further studies are required to confirm the effectiveness of these isolates as probiotics in aquaculture. Significance and Impact of the Study To the best of our knowledge, for the first time, the presence of probiotic candidates belonging to W. Oryzae was confirmed in fish intestinal microbiota.