The initial establishment of lactic acid bacteria (LAB) and bifidobacteria in the newborn and the role of breast-milk as a source of these microorganisms are not yet well understood. The establishment of these microorganisms during the first 3 months of life in 20 vaginally delivered breast-fed full-term infants, and the presence of viable Bifidobacterium in the corresponding breast-milk samples was evaluated. In 1 day-old newborns Enterococcus and Streptococcus were the microorganisms most frequently isolated, from 10 days of age until 3 months bifidobacteria become the predominant group. In breast-milk, Streptococcus was the genus most frequently isolated and Lactobacillus and Bifidobacterium were also obtained. Breast-milk contains viable lactobacilli and bifidobacteria that might contribute to the initial establishment of the microbiota in the newborn.
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