Bifidobacterium Species Colonization in Infancy: A Global Cross-Sectional Comparison by Population History of Breastfeeding

Abstract

<i>Bifidobacterium</i> species are beneficial and dominant members of the breastfed infant gut microbiome; however, their health benefits are partially species-dependent. Here, we characterize the species and subspecies of <i>Bifidobacterium</i> in breastfed infants around the world to consider the potential impact of a historic dietary shift on the disappearance of <i>B. longum</i> subsp. <i>infantis</i> in some populations. Across populations, three distinct patterns of <i>Bifidobacterium</i> colonization emerged: (1) The dominance of <i>Bifidobacterium longum</i> subspecies <i>infantis</i>, (2) prevalent <i>Bifidobacterium</i> of multiple species, and (3) the frequent absence of any <i>Bifidobacterium.</i> These patterns appear related to a country's history of breastfeeding, with infants in countries with historically high rates of long-duration breastfeeding more likely to be colonized by <i>B. longum</i> subspecies <i>infantis</i> compared with infants in countries with histories of shorter-duration breastfeeding. In addition, the timing of infant colonization with <i>B. longum</i> subsp. <i>infantis</i> is consistent with horizontal transmission of this subspecies, rather than the vertical transmission previously reported for other <i>Bifidobacterium</i> species. These findings highlight the need to consider historical and cultural influences on the prevalence of gut commensals and the need to understand epidemiological transmission patterns of <i>Bifidobacterium</i> and other major commensals.