Friday, June 22, 2012

How About A Fecal Transplant?

Yes, you read correctly.  A fecal transplant.  "Fecal" as in "poop."  "Transplant" as in "from one person to another."

This new medical procedure makes the idea of using leeches, maggots, and flesh-nibbling fish seem appetizingly appealing by comparison.  I recently learned about it from a couple of New York Times science articles by Carl Zimmer and Gina Kolata, and it was so interesting I did some followup investigating of my own. The transplant is one promising development in the treatment of all kinds of health problems that has emerged from the field of medical ecology, a branch of microbiology which studies the complex interactions between health and a person's microbiota (or microbiome), the collection of 100 trillion microbes that live on and in each human body.

The two to five pounds of complex microbial communities that inhabit our bodies are apparently essential to not just our health but to our very existence.  Without them we would be unable to digest food, synthesize certain vitamins, and fight off many infectious diseases.  While it is certainly true that quite a few bacteria are harmful to us, many more are beneficial to the point that we can't live without them.  Our microbiome is as essential to us as our heart or our brain.

A microbiome is a true ecosystem in the sense that it involves a complex balance among the many different species of bacteria, viruses and fungi that comprise it.  In fact, one difficulty in studying these organisms has been that they are so adapted to living surrounded by other microbes and are so dependent on their host body that many can't be isolated and grown in the lab, and even if they do survive outside of the body they often behave differently than in their natural environment. However, a recent five-year federally funded research program has begun to give a clearer picture of our microbial communities and their impact on our health by using DNA analysis that doesn't require laboratory cultures. Called the Human Microbiome Project, the study involves 200 scientists at 80 institutions who have sequenced the genetic material of bacteria taken from nearly 250 healthy people, an immense effort that has led to some surprising findings.

For one thing, the researchers discovered more strains than they had ever imagined — as many as a thousand bacterial strains on each person. And each person’s collection of microbes was different from the next person’s, a kind of microbial fingerprint that uniquely identifies each individual.  Also surprising was that there were genetic signatures of disease-causing bacteria and viruses lurking in the microbiome of every one of these healthy individuals.  Instead of making people ill, or even infectious, the disease-causing microbes were simply living peacefully among their neighbors, held in check by the complex interactions of the microbiome community.

Another finding is that a person's microbiome changes throughout life in response to environmental and biological influences.  This process begins at birth, when certain key bacteria are transferred from mother to child during delivery and afterward during nursing. In pregnancy the relative concentrations of certain bacteria change in a women's birth canal in response to hormonal shifts.  One species of bacteria that is normally rare but becomes dominant is lactobacillus johnsonii. It is usually found in the gut, where it produces enzymes that digest milk. It’s an odd species to find proliferating in the vagina, to say the least. Dr. Aagaard-Tillery, one of the scientists who made this discovery, speculates that during delivery a baby will be coated by lactobacillus johnsonii and ingest some of it, an inoculation that prepares the infant to digest breast milk. The milk, it turns out, contains some 600 species of beneficial bacteria and also certain sugars that the baby can't digest but which nourish the bacteria. It seems the mother is not only feeding the child but also the child's bacteria and thereby promoting the development of the child's microbiome.

Our cultural attitude toward microbes is decidedly negative and non-selective:  "The only good microbe is a dead microbe."  However, the more we learn about the microbiome the clearer it becomes that this is not really justified and may be very harmful to us in the end.  For example, the use of broad-spectrum antibiotics to treat infections, while effective in the short run, wipes out not only the bad bacteria but also many of the the ones that are necessary to restore and maintain health.  We have generally assumed that the microbiome would return to normal on its own, but scientists are now realizing that assumption isn't justified -- it would be like assuming that lettuce and tomatoes would spontaneously return after spraying the whole garden with herbicide to kill the weeds.  In fact, there appear to be certain strains of harmful bacteria that thrive in disrupted or diminished microbiomes following broad-spectrum antibiotic treatments, like the antibiotic-resistant Clostridium difficile.  Re-establishing a healthy microbiome is very difficult in these circumstances.

Enter the fecal transplant.

According to Lita Proctor, program director for the Human Microbiome Project, "Half of your stool is not leftover food. It is microbial biomass.”  Assuming the donor is healthy, this means stool contains the complex collection of microbes needed to restart a depleted microbiome in another person.  And it seems to work.  Initial studies using fecal suppositories to treat Clostridium difficile infections have been very promising, and larger clinical trials are underway.  Fecal transplants are also being studied as a way to treat obesity by transplanting fecal samples from lean donors to obese patients. Researchers at the Academic Medical Center in Amsterdam are running a clinical trial to see if fecal transplants can help treat obesity. They have recruited 45 obese men; some are getting transplants from their own stool, while others get transplants from lean donors. The scientists are finding that the transplants from lean donors are changing how the obese subjects metabolize sugar.

Efforts are also underway to isolate the bacteria from the poop, to remove the "ick" factor, as researcher Dr. Alexander Khoruts puts it.  He would eventually like to develop probiotic pills that contain just a few key species required to build the intestinal ecosystem  -- Poop Pills, so to speak.

I certainly learned a lot from researching this topic, and the information has changed my outlook about who and what I am. For one thing, I realize how wrong my belief is that I am separate and independent from my environment.  "I" am composed of trillions of other organisms without which I could not exist.  They are as much "me" as any other part of my body.  As Dr. Barnett Kramer of the National Cancer Institute has said,  "humans in some sense are made mostly of microbes. From the standpoint of our microbiome, we may just serve as packaging.”

Certainly a humbling thought.





5 comments:

Randy Phillips said...

Amazing and transformative information - please keep up the great research that was behind this and your other posts!

SimoneStan said...

Could it be that humans exist to provide the right environment for bacteria survival?

Richard Sherman said...

One comment I read was that the bacteria in our bodies are very simple because they have given up a lot of their metabolism function to us, the host. This means they benefit from keeping us healthy, and this may be the reason they have evolved in ways that keep our immune system functioning.

PaddleDoc said...

Many of our body "parts" may have been previously "free and independent" microbes that gave over functions to join in with the integrated parts we call our body, but your research points out this system we call ourselves is truly a community that ranges from totally dependent to sorta independent parts along for the ride! Mites and other critters abound in this zoo as well. The ick factor should become an oohh factor I suppose if we had proper appreciation of the total system.

Richard Sherman said...

A friend just wrote in an email a comment that is worth sharing (anonymously):

"Well, it certainly causes one to re think the "me---not me" boundary but also, what we mean when we say one is 'full of s--t!'"