Transmission of intestinal Bifidobacterium longum subsp. longum strains from mother to infant, determined by multilocus sequencing typing and amplified fragment length polymorphism

Abstract

The gastrointestinal tracts of neonates are colonized by bacteria immediately after birth. It has been discussed that the intestinal microbiota of neonates includes strains transferred from the mothers. Although some studies have indicated possible bacterial transfer from the mother to the newborn, this is the first report confirming the transfer of bifidobacteria at the strain level. Here, we investigated the mother-to-infant transmission of Bifidobacterium longum subsp. longum by genotyping bacterial isolates from the feces of mothers before delivery and of their infants after delivery. Two hundred seven isolates from 8 pairs of mothers and infants were discriminated by multilocus sequencing typing (MLST) and amplified fragment length polymorphism (AFLP) analysis. By both methods, 11 strains of B. longum subsp. longum were found to be monophyletic for the feces of the mother and her infant. This finding confirms that these strains were transferred from the intestine of the mother to that of the infant. These strains were found in the first feces (meconium) of the infant and in the feces at days 3, 7, 30, and 90 after birth, indicating that they stably colonize the infant's intestine immediately after birth. The strains isolated from each family did not belong to clusters derived from any of the other families, suggesting that each mother-infant pair might have unique family-specific strains.

Figures

Fig. 1.

Dendrogram derived from a comparison of MLST profiles of B. longum subsp. longum isolates from mothers' and infants' feces and breast milk for all 8 families. The dendrogram was generated with a multiscale setting for comparison and UPGMA for clustering. *, strains isolated from mothers' and infants' feces showing the same MLST profiles within a given cluster. **, strains isolated from breast milk and mothers' and infants' feces showing the same MLST profiles within a given cluster.

Fig. 2.

AFLP profiles of the 11 B. longum subsp. longum strains found by MLST analysis to be monophyletic between feces from mothers and their infants. Dendrograms were generated with a multiscale setting for comparison and UPGMA for clustering.