The increasing use of faecal transplants to treat Clostridium difficile bacterial infection urgently needs proper screening of donors, good long-term trials and monitoring in order to provide sensible advice to patients, experts said.
While "it is clearly better than further antibiotics for treating conditions like C difficile", claims that faecal transplantation could be a cure-all for many diseases "are probably too optimistic", the general medicine journal BMJ reported on Tuesday.
It cited professor Tim Spector from King's College London and professor Rob Knight from the University of California-San Diego.
An analysis of the evidence found an 85 percent success rate with faecal transplants compared with only 20 percent success for standard antibiotic treatment, Spector and Knight said.
A recent trial was stopped early because of the overwhelming superiority of faecal transplantation, with 90 percent success rate compared with 26 percent for powerful antibiotics.
But the experts cautioned that the use of faecal transplantation is being increasingly tested in other common conditions, including obesity, diabetes, irritable bowel syndrome, colitis and many others.
There are long term potential risks of transferring microbes to a new host, which could include transferring susceptibility to obesity and even mental illness, they said in a jointly written article.
"These possible risks suggest that faecal transplantation, although an exciting new tool, should be carefully monitored and refined to include most of the key beneficial microbes."
"We urgently need more expertise and centres, proper screening of donors and good long term trials and monitoring procedures in order to provide sensible advice," the trial showed.
In the faecal microbial transplantation, the liquidised stool (or its cryopreserved microbial content) of a healthy donor is introduced to the colon of the Clostridium difficile patient through a nasogastric tube or the rectum.
