Clostridia from preterm infants metabolize human milk oligosaccharides to suppress pathobionts and modulate intestinal function in organoids

Infant gut microbiome development is strongly impacted by breastmilk and human milk oligosaccharides (HMOs), which can protect preterm infants against pathologies including necrotizing enterocolitis. HMO metabolism in bifidobacteria is well characterized and linked to health outcomes, but the scope of HMO-utilizing species remains unclear. Here, using a combination of genomics, proteomics and metabolomics, we show that Clostridium species isolated from preterm infants (born at <32 weeks gestation), in particular Clostridium perfringens lacking the toxin perfringolysin O (PfoA), metabolized HMOs. Clostridium species produced beneficial metabolites including short-chain fatty acids and tryptophan catabolites at higher quantities than Bifidobacterium species in vitro. Cell-free supernatant from C. perfringens was non-toxic to colonic cell lines, promoted the growth of commensal bifidobacteria and inhibited growth of pathobionts isolated from the preterm infant gut in vitro. It also suppressed inflammation in preterm-derived intestinal organoids. These findings expand our understanding of HMO-metabolizing microbes and suggest that pfoA^- C. perfringens strains could contribute to healthy infant gut development.