Abstract: The aim of this experiment was to study the diversity of Bifidobacterium longum isolated from infant feces. Using modified MRS medium, bifidobacterial strains were isolated from the feces of healthy infants in Harbin. To identify and analyze the diversity of B. longum strains, we used physiological and biochemical experiments, 16S rDNA homology analysis, heat-shock protein 60 gene (hsp60) homology analysis, random amplified polymorphism DNA (RAPD) and multilocus sequence typing (MLST). Eighteen anaerobic strains were isolated, among which, 7 were identified as B. longum subsp. longum, and 3 as B. longum subsp. infantis according to morphology, physical and biochemical properties, 16S rDNA homology analysis and hsp60 homology analysis. The results of RAPD and MLST showed that the 7 strains of B. longum subsp. longum belonged to 6 genotypes while the 3 strains of B. longum subsp. infantis belonged to 2 genotypes. Overall, these results showed that there were differences in the diversity of B. longum isolated from infant feces.

Key words: Bifidobacterium longum, heat-shock protein 60 gene (hsp60), random amplified polymorphism DNA (RAPD), multilocus sequence typing (MLST)