The effects of administration of bifidobacteria on the intestinal microbiota in low-birth-weight infants, and the transition of each strain of administered bifidobacteria were investigated. A single strain of Bifidobacterium breve M-16V (5 × 10(8); one-species group) or a mixture of three species composed of B. breve M-16V, Bifidobacterium longum subsp. infantis M-63 and B. longum subsp. longum BB536 (5 × 10(8) of each strain; three-species group) were administered daily for 6 weeks. Bifidobacterial administration significantly increased the detection rates and cell numbers of bifidobacteria in the feces (weeks 1-6). The proportion of bifidobacteria was significantly higher in the one-species group at weeks 1-4, and in the three-species group at weeks 1-6 compared with the control group. Furthermore, the proportion of bifidobacteria in the three-species group was significantly higher than that in the one-species group at weeks 1 and 6. The proportion of infants with bifidobacteria-predominant microbiota was significantly higher in the three-species group than in the control group during the test period. The detection rates of Clostridium were lower in the bifidobacteria-administered groups. The proportions of Enterobacteriaceae were significantly lower in the three-species group compared to the other groups (weeks 4 and 6). Among the three strains administered, B. breve M-16V and Bifidobacterium infantis M-63 were detected in 85% or more of the infants during the administration period, while B. longum BB536 was detected in 40% or less. Compared with administration of one species, administration of three species of bifidobacteria resulted in earlier formation of a bifidobacteria-predominant fecal microbiota and maintenance of this microbiota.
Keywords: Bifidobacteria; Intestinal microbiota; Premature infant.
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