Longitudinal changes in bifidobacterial population during the first two years of life.

Early life microbiota encompasses of a large percentage of Bifidobacterium, while it is not sufficiently understood how the Bifidobacterium population develops after infant's birth. Current study investigated the longitudinal changes in Bifidobacterium population during the first two years of life in 196 term born infants (1,654 samples) using 16S rRNA-23S rRNA internal transcribed spacer (ITS) sequence analysis. Throughout the first two years of life, Bifidobacterium breve, Bifidobacterium longum subsp. longum and Bifidobacterium adolescentis were most dominant and prevalent in the Bifidobacterium population, while B. breve had the highest relative abundance and prevalence during the first week of life and it was taken over by B. longum subsp. longum around two years after birth. Sampling time points, early antibiotic(s) exposure (effect only measurable within a month after birth), delivery mode (effect still detectable two-months after birth) and feeding mode (effect lasted until six months after birth), significantly contributed to the overall variation in the bifidobacterial population. From six months onwards, introducing of solid food and cessation of breastfeeding were accompanied with drastic changes in the composition in bifidobacterial population. Altogether, current study confirmed the effect of potential contributors to the longitudinal changes within the bifidobacterial population during the first two years of life. Registered at https://clinicaltrials.gov: NCT02536560.