Stunting is associated with persistent and transferable alterations in the gut microbiome.

As robust animal models to study the pathophysiology of stunting are absent, we have comparatively characterized the gut microbiota of malnourished/stunted vs. clinically healthy/normal Kenyan toddlers (12-24 months old) and established a gnotobiotic (Gn) pig fecal transplant model to gain understanding of microbial community structure associated with stunting. As expected, the bacterial composition between the two toddler groups was distinct: Actinobacteria was most prevalent in healthy toddlers, whereas Proteobacteria dominated in stunted toddlers. Although the diversity indices showed no significant differences, unique bacterial genera were found in each toddler group: three genera unique to stunted toddlers and ten unique to healthy toddlers, with eight genera shared between the groups. We observed a higher number of enriched bacterial virulence genes in healthy vs. stunted toddlers suggesting that the microbiome plasticity and functional characteristics of the healthy toddlers allow for the pathogen/pathobiont control. In contrast, we noted the presence of more genes associated with antimicrobial-resistance (AMR) bacteria in stunted toddlers, possibly due to early-life antibiotic treatments. Of interest, functional analysis showed that CAZymes associated with carbohydrate biosynthesis, and a few metabolic pathways related to protein/amino acid, carbohydrate and fat catabolism were enriched in stunted toddlers. In contrast carbohydrate degradation CAZymes and numerous anabolic pathways were prevalent in healthy toddlers. These patterns were also evident in the Gn pigs transplanted with stunted/healthy human fecal microbiota (HFM). Overall, our findings suggest that the microbiota transplanted Gn pigs represent a valuable model for studying the infant microbial community structure and the impacts of stunting on the child gut microbiota. Additionally, this is the first study to demonstrate that the healthy vs. stunted microbiota composition and function remained different in the Gn pigs throughout the study. This information and the Gn pig model are vital for developing and testing targeted interventions for malnourished/stunted populations, consequently advancing microbiome-based diagnosis and personalized medicine.