Faecal transplant. Yes, it means what it says. It involves taking faeces (let's be blunt, poo) from a healthy person and transplanting it into the gut of another person. Why would anyone do that? Studies are showing it may be of help where the recipient has an overgrowth of the bacterium Clostridium difficile in their gut.

Your bowel is home to trillions of bacterial cells. During times of infection or chronic disease, the makeup of your gut microbiota can change for the worse, and the idea behind faecal transplants is to take the microbes in a “healthy” stool and put them in the recipient’s bowel to build up a healthier balance of bugs there.

An old idea
Such transplants were used decades ago in western medicine as "faecal enemas" in the mid-20th century, notes Prof Fergus Shanahan, a consultant gastroenterologist at Cork University Hospital and professor of medicine at University College Cork.

“It’s an old idea,” he says. “People had stumbled upon the fact that if you gave someone a faecal enema, they could restore what they termed the ‘flora’ in the gut. But then it became difficult to do for ethical and safety reasons.”

Since then though, our understanding of gut microbes has exploded, and faecal microbiota transplantation (FMT) is coming into vogue again, at least for research – though to Shanahan's knowledge it is not being carried out in Ireland.

So far the cases have predominantly involved patients who have an overgrowth of C. difficile , which in severe cases can be fatal or can mean the patient has to have part of the bowel removed.

A recent study led by the University of Amsterdam put faecal transplants to the test in patients who had recurrent problems with C. difficile , comparing it with antibiotic treatments.

Does it work?
The measure of success was that the diarrhoea associated with the infection would stop, and that happened in 15 out of the 16 patients who got transplants (the majority just needed one), compared with four out of 13 patients who were just on antibiotics. The results were published earlier this year in the New England Journal of Medicine .

So how does it work? Infusing a preparation of healthy donor stool into the recipient's gut could introduce a kind of bacterial "rent-a-crowd" to compete with C. difficile , explains Prof Shanahan.

"It probably means that C. difficile becomes not a dominant species but a minority species," he says. "You may ultimately revert back to your original microbiota, but it gives you more time to overcome the C. difficile."

Not for everyone
But he stresses that faecal transplant is not for everyone, because there are potential risks too. "We have known for a long time that certain combinations of bacteria can be harmful and may even raise the risk of colon cancer in the longer term," he says.

“So if you are an elderly patient and quite ill with it and it can’t be eliminated by other forms of treatment, in my view it becomes a realistic proposition. But that does not mean that it is something that should be loosely given to all.”

Another option could be to transplant the bugs themselves, rather than the whole faecal package. But what bugs would they need to be? Shanahan and colleagues at the Science Foundation Ireland-funded Alimentary Pharmabiotic Centre in Cork are looking to figure out the "minimum microbiota" needed to offer protection.

“There are at least 1,000 species in a normal gut microbiota, but you don’t necessarily need 1,000 different species to get protection,” he says. “We want to identify what is the minimum number, and can we sequence them and understand them so that we know precisely what we are giving, rather than using whole faeces.”