Gut microbiome function and composition in infants from rural Kenya and association with human milk oligosaccharides

Abstract

The gut microbiota evolves rapidly after birth, responding dynamically to environmental factors and playing a key role in short- and long-term health. Lifestyle and rurality have been shown to contribute to differences in the gut microbiome, including <i>Bifidobacterium</i> levels, between infants. We studied the composition, function and variability of the gut microbiomes of 6- to 11-month-old Kenyan infants (<i>n</i> = 105). Shotgun metagenomics showed <i>Bifidobacterium longum</i> to be the dominant species. A pangenomic analysis of <i>B. longum</i> in gut metagenomes revealed a high prevalence of <i>B. longum</i> subsp. <i>infantis</i> (<i>B. infantis</i>) in Kenyan infants (80%), and possible co-existence of this subspecies with <i>B. longum</i> subsp. <i>longum</i>. Stratification of the gut microbiome into community (GMC) types revealed differences in composition and functional features. GMC types with a higher prevalence of <i>B. infantis</i> and abundance of <i>B. breve</i> also had a lower pH and a lower abundance of genes encoding pathogenic features. An analysis of human milk oligosaccharides (HMOs) classified the human milk (HM) samples into four groups defined on the basis of secretor and Lewis polymorphisms revealed a higher prevalence of HM group III (<i>Se+, Le</i>-) (22%) than in most previously studied populations, with an enrichment in 2'-fucosyllactose. Our results show that the gut microbiome of partially breastfed Kenyan infants over the age of six months is enriched in bacteria from the <i>Bifidobacterium</i> community, including <i>B. infantis</i>, and that the high prevalence of a specific HM group may indicate a specific HMO-gut microbiome association. This study sheds light on gut microbiome variation in an understudied population with limited exposure to modern microbiome-altering factors.