摘要：Bifidobacterium 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
Bifidobacterium in breastfed infants around the world to consider the potential impact of a historic dietary shift on the disappearance of
B. longum subsp.
infantis in some populations. Across populations, three distinct patterns of
Bifidobacterium colonization emerged: (1) The dominance of
Bifidobacterium longum subspecies
infantis, (2) prevalent
Bifidobacterium of multiple species, and (3) the frequent absence of any
Bifidobacterium. 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
B. longum subspecies
infantis compared with infants in countries with histories of shorter-duration breastfeeding. In addition, the timing of infant colonization with
B. longum subsp.
infantis is consistent with horizontal transmission of this subspecies, rather than the vertical transmission previously reported for other
Bifidobacterium 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
Bifidobacterium and other major commensals.
