This doctor is on the hunt for people with first-rate faeces

Faecal transplants are now commonly used to treat recurrent Clostridioides difficile infections, but finding people whose faeces are of sufficient quality to be used in these transplants is a major challenge.

“It’s actually quite a frustrating activity because only about 1 per cent of people who respond to advertisements for donors are healthy enough,” says Elizabeth Hohmann, an infectious disease expert at Massachusetts General Hospital in Boston. “I ask them to keep coming back to donate because they’re very hard to find.” Over the years, some of her donors have supplied more than 100 of their precious stools.

Hohmann has been in charge of faecal transplants at the hospital for 15 years. It is her job to collect donated stools and turn them into oral capsules, which are then given to people with hard-to-treat gut conditions, like recurrent C. difficile infections that cause diarrhoea and haven’t responded to antibiotics. The “good” gut bacteria from the donor faeces help to edge out the “bad” bacteria in the recipients’ guts, often alleviating their symptoms.

To find donors, Hohmann posts ads online offering $1200 for a month’s worth of stool donations.

First, respondents undergo extensive screening. Most are let go at the initial phone interview stage because they don’t meet certain criteria. For example, they cannot be healthcare workers or have recently travelled to South-East Asia, since both increase the chance of picking up drug-resistant gut bacteria. They must also be lean, because in the past, faecal transplants from donors with obesity have led to the development of the condition in recipients.

Those who pass this initial screening then undergo a battery of tests, including various blood tests to assess their overall health, tests for infections like HIV and covid-19, and a rectal exam to check for bleeding or other abnormalities that may signal gut troubles.

Hohmann says her best donors tend to be exercise enthusiasts with healthy diets. For example, one of her regulars is “a semi-professional athlete who is a personal trainer and gym manager”. Top-notch stools are generally associated with diets rich in fresh fruit, vegetables and whole grains, with minimal ultra-processed foods, she says. “I know one [faecal transplant centre] was talking about only using vegan donors, but actually the best donors I’ve had have been omnivores,” she says.

A typical donation period lasts two to four weeks. During this time, the donor defecates at the hospital as many times as possible. “Often, they have very regular bowel movements so they come into the hospital at the same time each day and drink a coffee to get things going,” says Hohmann. Each stool is caught by a plastic container placed in the lab toilet.

Hohmann immediately converts the fresh stool into capsules. “I put it in a blender with saline, then filter it through graded mesh filters,” she says. After several more processing steps, she pipettes the liquid into capsules. “It’s not pleasant, but it’s something you kind of get used to,” she says.

Afterwards, the donors are screened once more to check they haven’t picked up covid-19 or other infections since their initial screening. “You want to make sure they haven’t picked up Salmonella from eating at a terrible restaurant or something,” she says. If they have, the capsules must be destroyed and Hohmann has to start all over again with another donor.

Despite these occasional setbacks, Hohmann says she loves the work because of the transformative results she sees in faecal transplant recipients. For example, she recently had a patient who was so sick he couldn’t work. Since taking the stool capsules, he has been able to work 30 hours a week. “I keep doing it because, you know, it really does make a huge difference in some people’s lives,” she says.

Unfortunately though, now that Hohmann is nearing retirement, she is struggling to find a successor. “I keep asking my division, ‘who wants to help out?’. Nobody. It’s silent. They hear about the basics of it and they’re just totally grossed out.”