Probiotic potential and safety assessment of Lactobacillus isolated from yaks.

Current problem of antibiotic resistance and the high incidence of bacterial diseases has brought huge losses to the yak breeding industry in Tibet. Therefore, the purpose of this study was to isolate Lactobacillus with safety and beneficial probiotic potential for the prophylaxis of intestinal diseases in yaks. After 16S rDNA sequence, four strains i.e. Lactobacillus sakei (named L4), Enterococcus hirae (named E5), Pediococcus acidilactici (named P7), Weissella confusa (named W8) were isolated from feces of yaks. The results of tolerance to acid, bile salt, enzyme and temperature showed that P7 was highly tolerant to acid, bile salt and digestive enzyme, while E5 was more resistant to temperature. The antibacterial assay showed L4 had a strong inhibitory effect against Staphylococcus aureus (BNCC186335), and E5, P7, W8 had effective antibacterial ability against Escherichia coli (C83902). In addition, L4, E5, P7 and W8 mainly produced organic acids and bacteriocin production to inhibit common intestinal pathogens. The results of antibiotic susceptibility assay indicated that L4, E5, P7 and W8 were highly sensitive to most clinically used antibiotics and didn't contain the VanA and VanB genes on the basis of PCR amplification, and L4, E5, P7 and W8 didn't exhibit hemolytic activity. The animal toxicity experiment results showed that no obvious pathological change was found in intestinal tissue sections, and L4, E5 and W8 strains also promoted the growth performance of mice, consequently, the L4, E5, P7 and W8 had no toxic effect on mice. In conclusion, lactobacillus isolated from feces of yaks not only have potential probiotics and strong antibacterial ability in vitro, but also are safe. Therefore, they have the potential to reduce the occurrence of bacterial diseases as new feed additives.