Abstract
Bifidobacteria are important members of human gut microbiota; however, quantitative data on their early-life dynamics is limited. Here, using a sensitive reverse transcription-qPCR approach, we demonstrate the carriage of eight signature infant-associated Bifidobacterium species (B. longum, B. breve, B. bifidum, B. catenulatum group, B. infantis, B. adolescentis, B. angulatum and B. dentium) in 76 healthy full-term vaginally-born infants from first day to three years of life. About 21% babies carry bifidobacteria at first day of life (6.2 ± 1.9 log10 cells/g feces); and this carriage increases to 64% (8.0 ± 2.2), 79% (8.5 ± 2.1), 97% (9.3 ± 1.8), 99% (9.6 ± 1.6), and 100% (9.7 ± 0.9) at age 7 days, 1, 3 and 6 months, and 3 years, respectively. B. longum, B. breve, B. catenulatum group and B. bifidum are among the earliest and abundant bifidobacterial clades. Interestingly, infants starting formula-feed as early as first week of life have higher bifidobacterial carriage compared to exclusively breast-fed counterparts. Bifidobacteria demonstrate an antagonistic correlation with enterobacteria and enterococci. Further analyses also reveal a relatively lower/ delayed bifidobacterial carriage in cesarean-born babies. The study presents a quantitative perspective of the early-life gut Bifidobacterium colonization and shows how factors such as birth and feeding modes could influence this acquisition even in healthy infants.
Highlights
Bifidobacteria represent one of the earliest and most abundant bacterial colonizers of the neonatal gut and are well known to confer a myriad of benefits to the host intestinal, metabolic and immune health[1,2,3,4,5,6,7]
We aimed to define the quantitative profile of gut bifidobacterial microbiota during early life in a relatively large cohort of 76 healthy full-term vaginally-born Japanese infants by employing a sensitive analytical approach based on reverse transcription-quantitative-PCR (RT-qPCR) targeting bacterial 16 S rRNA molecules
In our previous methodological studies, we have validated that the counts obtained by this RT-qPCR system are equivalent to the bacterial counts obtained by culture and fluorescent in-situ hybridization (FISH) methods irrespective of the bacterial growth phase[17, 18], and that the analytical sensitivity of RT-qPCR is approximately 100- to 1000-fold higher than that of other molecular methods including qPCR and T-RFLP17, 18, 20, 22
Summary
Bifidobacteria represent one of the earliest and most abundant bacterial colonizers of the neonatal gut and are well known to confer a myriad of benefits to the host intestinal, metabolic and immune health[1,2,3,4,5,6,7]. While the genus Bifidobacterium is comprised of more than 50 species/subspecies, the typical human-associated species include B. bifidum, B. breve, B. longum, B. infantis, B. catenulatum, B. pseudocatenulatum, B. adolescentis, B. angulatum, B. dentium, and B. pseudolongum[4, 5, 7, 9, 10] Despite their perceived significance, the precise succession ontogeny of these bifidobacterial species during infancy and early childhood remains to be comprehended, in terms of their actual population levels i.e., the absolute bacterial count. Most formula-feed supplements presently prevalent in Japan are fortified with different prebiotics such as galacto-oligosaccharides, fructo-oligosaccharides, lactulose, raffinose etc.; the data on the influence of these compounds on the fecal bifidobacterial levels during infancy remain limited In these contexts, we aimed to define the quantitative profile of gut bifidobacterial microbiota during early life in a relatively large cohort of 76 healthy full-term vaginally-born Japanese infants by employing a sensitive analytical approach based on reverse transcription-quantitative-PCR (RT-qPCR) targeting bacterial 16 S rRNA molecules. The data provide important numerical information about the population levels (i.e. the actual bacterial count) of human gut bifidobacterial community during infancy and early childhood and shall be informative and facilitative for prospective microbiota-related studies
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