Screening of Lactobacillus from breast milk and infant feces and evaluation of their bile salt tolerance

The intestinal bile salt concentration of infants is lower than that of adults, and the necessary bile salt tolerance of probiotics for infants remains unclear. In this study, Lactobacillus strains were isolated from breast milk and infant feces. The strains with better bile salt tolerance were screened, and their bile salt tolerance was compared with Lactobacillus strains from the adult intestine. The results showed that the bile salt concentration had a better distinguishing effect when it was 0.075 and 0.1%. Among the 28 strains of Lactobacillus with better bile salt tolerance, there were 16 strains of Lactobacillus plantarum, among which eight strains had greater than 70% survival under 0.075% bile salt and two strains had more than 50% survival under 0.1% bile salt. L. plantarum strains iso-lated from breast milk and infant feces had a significantly lower survival rate than those isolated from the adult intestine (P < 0.05) under 0.1% bile salt, while there was no significant difference in the survival rate under 0.075% bile salt (P > 0.05). Therefore, the demands for bile salt tolerance of probiotics for infants might be lower than that for adults. It is suggested that the standard for the screening of probiotics from breast milk and infant feces should differ from adults.