A synthetic gut microbiome could replace stool transplants
A stool transplant from a young donor can fully reset the gut microbiome of an older recipient. But regulation makes it increasingly difficult. Researchers are now trying to achieve the same effect with a precisely formulated mixture of bacteria.
In a faecal microbiota transplant (FMT), stool from a healthy donor is transferred to a patient. Animal studies show clear health benefits when old animals receive microbiomes from young donors. The problem is that every donor has a unique composition of gut bacteria. That makes standardisation hard, and regulators like the FDA demand standardisation before approving medicines. The researchers took a step toward an alternative: a live biotherapeutic product (LBP) with a known, defined composition of bacterial strains.
In a small clinical study with 18 participants, they compared this product with standard FMT, both derived from the same donor. The participants had recurrent Clostridioides difficile infection, a serious gut infection that often follows antibiotic use. Safety and efficacy were comparable between the two treatments. The bacterial strains engrafted durably in recipients’ guts in both cases.
How far are we from an artificial microbiome?
The current product contains fifteen bacterial strains. A healthy human microbiome contains hundreds to thousands. That gap is large. But the researchers see this as a first step: if a fifteen-strain mixture can be produced under controlled manufacturing conditions, the path toward larger mixtures is open.
This is relevant for aging research because the gut microbiome of older people differs structurally from that of younger people. Shifting toward a younger microbiome via FMT has measurable effects in animal models, including on inflammation and cognition. Whether a standardised LBP can achieve the same in humans is a question for future research.
Regulation as a brake on innovation
The FDA has approved only one FMT product, for use in Clostridioides difficile infection. Other applications, such as resetting an aged microbiome, fall outside that approval. A standardised bacterial mixture partially sidesteps that problem: it is reproducible and verifiable, which regulators can assess more readily than a product based on human stool.