Isolation and a survey on probiotic properties of Lactobacillus in rainbow trout (Oncorhynchus mykiss) intestine and their antibacterial properties against Yersinia ruckeri

Lactobacillus is the most common probiotic bacteria. The aim of this study was to isolate and evaluate the probiotic properties of rainbow trout (Oncorhynchus mykiss) intestinal Lactobacillus and to improve the digestive tract of this fish. After preparation of 75 rainbow trout, their intestinal contents were cultured in MRS broth medium and 56 Lactobacillus colonies were identified by biochemical tests. Lactobacillus strains were identified by biochemical tests and polymerase chain reaction (PCR), and their antibacterial activity, susceptibility to antibiotics, bile resistance and acidic conditions (pH=3) was evaluated. A total of six Lactobacillus strains Lactobacillus acidophilus, Lactobacillus reuteri, Lactobacillus animalis, Lactobacillus fermentum, Lactobacillus leishmania and Lactobacillus delbrueckii were identified. The antibacterial activity of Lactobacillus leishmania against Yersinia ruckeri was significantly (p˂0.05) higher than the antibiotic Enrofloxacin. (p˂0.05). All isolates were resistant to oxacillin and vancomycin antibiotics and were sensitive to tetracycline. Lactobacillus animalis, Lactobacillus acidophilus and Lactobacillus delbrueckii showed the highest resistance to bile (p˂0.05), respectively, and Lactobacillus acidophilus showed the highest resistance to acidic conditions. According to the results there are probiotic Lactobacillus in the rainbow trout digestive tract, and among them Lactobacillus acidophilus, Lactobacillus reuteri and Lactobacillus delbrueckii have better probiotic properties.