There are plenty of people who are exceptional in one way or another. But a new review published this week suggests that even the poo we make can be extraordinary. It argues that some of us are super faecal transplant donors, with poo that is uniquely suited to treating digestive and gut problems.
Our excrement is filled to the brim with countless species of bacteria. The bacteria comes from the gut through which the poop passes, a living world that we call the gut microbiome. Gross as it might be to imagine, this microbiome actually helps our body digest food and otherwise stay healthy. But the microbiome can sometimes go out of whack, leading to any number of digestive or neurological problems. One of these problems is chronic diarrhoea caused by infections of the bacteria Clostridium difficile.
In recent years, faecal microbiota transplantation (FMT) has been recognised as a way to restore a person’s unbalanced microbiome (usually, the donor poo is delivered via enema). When it comes to recurrent C. difficile infection, reported cure rates of FMT have been as high as 90 per cent and above, an astounding feat given how little success other treatments have had. That’s led doctors to hope that FMT could be a panacea for all sorts of conditions linked to the gut microbiome, like inflammatory bowel disease (IBD) or even type 2 diabetes. But the reality hasn’t been as encouraging; reported treatment rates for other conditions using FMT haven’t been anywhere near as high as they are for recurrent C. difficile infection.
Studies of FMT for C. difficile and these other conditions have spotted a peculiar pattern, though. Some donors seem to have especially great poo, with successful treatment rates from these donors being much higher than average. That’s led doctors to theorise about the existence of super-donors. The new review, published this week in Frontiers in Cellular and Infection Microbiology, took a look at these studies and tried to suss out what could make these donors special.
“We see transplants from super-donors achieve clinical remission rates of perhaps double the remaining average,” said senior author Justin O’Sullivan, a biologist at the University of Auckland in New Zealand, in a statement. “Our hope is that if we can discover how this happens, then we can improve the success of fecal transplantation and even trial it for new microbiome-associated conditions like Alzheimer’s, multiple sclerosis and asthma.”
There were a few factors that rose to the top in these donors. Compared to others, their poo had a robust, diverse mix of bacteria, including “keystone” species that help the body make important proteins or chemicals.
“In inflammatory bowel disease and diabetes for example, keystone species that are associated with prolonged clinical remission produce butyrate – a chemical with specialised functions in regulating the immune system and energy metabolism,” O’Sullivan said. His team also found a small study in which specially selected poo, high in bacteria called Lachnospiraceae and Ruminococcaceae, was used to successfully treat cases of recurrent hepatic encephalopathy, a brain condition caused by toxins that aren’t filtered out by the liver, in all 10 patients.
It’s probably not just about the bacteria, though. The guts of people who get transplants from these super donors often don’t look exactly the same, suggesting there are other factors influencing how well the transplant will take. A recipient’s genetics, innate immune system, and diet could affect that success, O’Sullivan and his team say. Even viruses that call our gut bacteria home might be playing a role.
“These viruses could affect the survival and metabolic function of transplanted bacteria and other microbes,” he said.
So far, FMT research in people has been limited to small studies and trials, making it hard to be sure of anything, including whether super donors are real. But things are changing. Just last week, the National Institutes of Health announced a randomised, controlled trial of FMT for recurrent C. difficile infection that will enrol more than 150 volunteers. Other recent studies have shown that more palatable transplant options, like a capsule taken orally, can work just as well as the typical, more invasive enema used for a transplant.
That option, coupled with a more detailed recording of the people involved in these studies (both donors and recipients), should make it much easier to conduct the research we need to better understand and refine faecal transplantation, the authors said. [Frontiers in Cellular and Infection Microbiology via Frontiers]
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