How Fecal Transplants Work

Bacteria are arguably the most successful life-forms on Earth. You can find them clustered around deep-sea vents, buried far underground or teeming throughout larger organisms, including us. Our mouths alone contain hundreds to thousands of species, divided into colonial neighborhoods across our teeth, gums and tongue. Our lungs, once thought microbe-free, house 2,000 per square centimeter, and our guts could host as many as 25,000-30,000 different species [sources: Grady; Zimmer].

While we might think of them as microscopic menaces -- the sources of such delights as bacterial meningitis, urinary tract infections and food poisoning -- without bacteria, life as we know it would not exist. Starting 2.7-2.8 billion years ago, cyanobacteria released the first oxygen into the atmosphere; today, bacteria convert atmospheric nitrogen into something plants can use and recycle nutrients from dead organisms into the ecosystem [sources: Biello; Ingham; Farquhar, Bao and Thiemens].

Bacteria and other microbiota perform similar functions in our bodies. Gut microbes produce vitamins and reduce tough plant compounds into digestible slurry [source: Zimmer]. Within the immune system, bacteria help maintain skin's protective qualities, and nasal microbes produce an antibiotic shield against airborne germs. Moreover, microbes keep the immune system in check by limiting harmful swelling. It isn't a stretch to see how they might therefore play a role in inflammation-associated disorders, such as obesity, cardiovascular disease, type 2 diabetes and inflammatory bowel disease (IBD) [sources: Gewirtz; Zimmer; Zimmer].

Microbes also make healthier babies. Breast milk packs 600 species of bacteria and provides sugars that feed a baby's developing gut bacteria [sources: Hunt et al.; Zimmer; Zivkovic et al.]. According to a June 2011 PLoS One study, a woman's vaginal microbiome changes drastically when she becomes pregnant. Among other effects, this new environment might prepare newborns to digest breast milk [sources: Aagaard et al.; Zimmer]. Some studies suggest children born via cesarean section might be more prone to skin infections from methicillin-resistant Staphylococcus aureus (MRSA), a staph germ that resists first-line antibiotics such as penicillin and amoxicillin. Such children could also face greater risk of developing allergies or asthma [sources: CDC; Zimmer].

Exposure to certain microorganisms trains a child's developing immune system [source: Zimmer]. It also probably provides a natural defense against inflammatory bowel disease (IBD), a chronic or recurring inflammation of the gastrointestinal tract caused by a haywire immune response [sources: Olszak et al.; Zimmer]. IBD, which includes ulcerative colitis and Crohn's disease, ranks among the five most widespread gastrointestinal diseases in the United States and racks up health care costs of $1.7 billion annually [source: CDC].

When the stakes are so high, particularly for patients with life-threatening intestinal maladies, doctors have started thinking outside the box -- and inside the colon.

Although something like it might have been practiced as far back as fourth-century China, modern fecal transplantation was pioneered in 1958 by Dr. Ben Eiseman at Denver General Hospital [sources: Allen; Brandt; Eiseman]. Fecal transplants saw only sporadic use for decades afterward, but began coming into their own around 2000 [sources: Allen; Brandt].

Here's how they work: After screening a donor for HIV, hepatitis and other disease-causing germs, the doctor dilutes a stool sample with saline or 4 percent milk, and then blends it into a milkshake-like slurry [sources: Allen; Bakken et al.; Floch; Silverman, Davis and Pillai]. The mixture is then fed into a patient's digestive tract via nasogastric or nasoduodenal tubes, through a colonoscope or via a retention enema [sources: Allen; Bakken; Hudson]. A nasogastric tube feeds matter through the nasal passage, down the throat and into the stomach; a nasoduodenal tube extends a bit farther.

The patient prepares for the procedure via the traditional take-no-prisoners, date-with-the-thunder-bucket ritual used by colonoscopy patients [sources: Allen; Stein]. Stool donations usually come from family members or spouses, but some facilities have tried unrelated, prescreened donors [source: Allen; Brandt].

If a fecal transplant sounds like a great DIY project, it isn't. First, stool is a level 2 biohazard; second, if you don't test fecal samples for communicable diseases, you could end up in a world of hurt; third, remind us to never drink frozen margaritas at your house [source: Bakken et al.; Floch; Silverman, Davis and Pillai].

As of October 2012, U.S. insurance does not cover fecal transplants, but some doctors believe billing codes for the procedure will exist by early 2013, with Medicare coverage following a similar schedule [sources: Allen; Brandt; Gewirtz]. Dr. Andrew Gewirtz of the Georgia State University Center for Inflammation, Immunity & Infection agrees.

"I would guess it might be insurable soon -- although it is possible that use of specific, defined bacterial cocktails may supplant it eventually," he says.

The procedure's legal status may pose a greater challenge. According to Dr. Lawrence Brandt of the Albert Einstein College of Medicine, the U.S. Food and Drug Administration (FDA) has declared feces for fecal microbiota transplants a drug, which makes transplants -- already a fringe therapy -- illegal until the FDA approves their use. While doctors are unlikely to do time for performing the procedure, its dodgy status could work against them should a malpractice suit arise [source: Brandt].

On the plus side, drug classification could move fecal transplants further into the mainstream. To become a widely accepted medical practice, the process must be subjected to large-scale clinical trials, but gaining funding for such trials from, say, the National Institutes of Health (NIH), hinges upon the FDA granting a substance "investigational status." Classification as a drug places feces in a category that the FDA recognizes for this purpose [sources: Brandt; Khoruts; McKenna].

Once they work the bugs out, bacteriotherapy and fecal transplantation could offer hope to a lot of sick people.

We stand on the threshold of a microbiotic renaissance, according to some physicians and microbiologists. As our understanding of this long-neglected field expands, so too will our treatment options.

As we mentioned, the place to start -- at least where fecal transplantation is concerned -- remains Clostridium difficile. According to the CDC, C. difficile infections kill 14,000 people in the United States annually, and its occurrence among hospitalized patients more than doubled from 2000 to 2009 [sources: Hudson; Zimmer]. One long-term follow-up study of 77 fecal transplant patients reported a 91 percent cure rate after just one fecal transplant, and a 98 percent cure rate with additional probiotics, antibiotics or fecal transplants [source: Brandt et al.].

Fecal microbiota might also hold answers for people with metabolic syndrome -- a collection of co-occurring risk factors, such as insulin resistance and extra weight around the middle, that increases the chance of coronary artery disease, stroke and type 2 diabetes [source: A.D.A.M.]. In some studies, fecal transplantation in metabolic syndrome patients reduced triglyceride levels and improved insulin sensitivity [source: Allen; Gewirtz].

Scientists have also tied obesity in rats to changes to the gut's microbiome. The intestines of obese persons contain a different set of microbes than those of non-obese persons, and clinical trial results suggest lean donors might help obese recipients lose weight by changing how they metabolize sugars [source: Zimmer].

"The composition and activity of gut microbiota is different in lean and obese individuals," says Dr. Alexander Khoruts, associate professor of medicine at University of Minnesota. "We know that animal energy metabolism can be changed by fecal microbiota transplantation. It is possible there will be something along these lines in humans."

"However, it is also clear that diet and lifestyle choices influence the composition of gut microbiota."

Indeed, we're only beginning to grasp the possibilities for fecal transplants and macrobiotics in general [source: Khoruts]. Don't confuse the two, however. Gut flora, though numerous, represent only a portion of total body microbes. Moreover, we do not yet fully understand the relationships between microbiota, health and disease, whether in the intestines or outside of them.

For example, a number of medical conditions may be linked to the intestine, including liver disease, migraines, chronic fatigue, rheumatoid arthritis, multiple sclerosis, Alzheimer's disease and Parkinson's disease, but how (or if) they relate to microbial therapy or fecal transplants remains unclear and will require substantial studies to answer [sources: Allen; Borody; Borody; Khoruts].

In the meantime, don't be too quick to "poo-poo" the idea of fecal transplantation. It's effective, fast and seems to have no side effects. But, as with any new therapy, we'll have to wait and see how it comes all out in the end.