Human Intestinal Flora and Fecal Transplantation

The human body contains at least ten times more bacterial cells than human cells. This is possible because bacteria have smaller cells than humans and the bacteria colonize cavities in our bodies. Most bacteria live in the large intestine, where they are accompanied by a smaller number of yeasts and other microscopic organisms. The microorganisms in the intestine are known as intestinal flora.

A community of microbes on or in the human body is called a microbiome. Scientists are gradually learning how important our intestinal microbiome is to our health. Serious problems can result from the wrong mix of microbes in the intestine. Fecal transplantation is a technique that is sometimes used to treat severe intestinal problems. A sample of feces from someone with beneficial intestinal flora is inserted into the large intestine of the patient, where the good microbes multiply. As unpleasant as fecal transplantation sounds, it's a very effective treatment for some people's health problems.

It’s thought that between 500 and 1000 different kinds of bacteria and trillions of individual bacteria normally live in the large intestine. Most of the microorganisms in the intestine are helpful, but some may be harmful. A healthy gut has far more beneficial microbes than harmful ones.

The relationship between the human host and the helpful microorganisms is mutualistic – both benefit from the relationship. For example, bacteria feed on nutrients that enter the large intestine from the small intestine, and they have a warm, moist area in which to live. The bacteria benefit us by producing nutrients that we absorb, such as vitamin K and biotin. In addition, some bacteria ferment the soluble fiber that we eat into short-chain fatty acids. These acids have many beneficial effects, including enhancing the activity of the immune system, improving the structure and function of the intestine lining, lowering the blood cholesterol level, and helping to regulate the blood glucose level. Good bacteria prevent the growth of pathogens (disease-causing microbes) in the large intestine and break down material that we are unable to digest.

There’s still a lot to be learned about the inhabitants of the large intestine and the roles that they play in our bodies. Scientists know that the human body contains a huge collection of microbes but have many questions about the identity of the microbes, how the microbes help us and the effects – either beneficial or detrimental – of the microbes on disease.

In 2008 the National Institutes of Health in the United States launched the Human Microbiome Project (HMP), which is intended to last for five years. In this project researchers want to identify and catalogue the microorganisms found on the skin and in the body’s cavities and to discover the functions of these microbes in health and disease.

Some patients with Crohn’s disease, ulcerative colitis or a Clostridium difficile infection have responded very well to fecal transplantation. Crohn’s disease and ulcerative colitis are forms of inflammatory bowel disease. In Crohn’s disease, any section of the gastrointestinal tract may be inflamed, from the mouth to the anus, although the lower part of the small intestine and the large intestine are the most common sites affected. Patches of inflamed tissue appear on the intestinal lining. In Crohn's disease and in ulcerative colitis the patient's immune system behaves abnormally in the digestive tract. Crohn’s disease may have mild symptoms or may have severe symptoms that make life very difficult and unpleasant. Gastrointestinal tract problems can include bloody diarrhea and abdominal pain, but symptoms may extend beyond the GI tract. The patient may suffer from loss of appetite, weight loss, fatigue, joint pain, fever, nausea, vomiting, skin problems and eye inflammation.

Ulcerative colitis has similar symptoms to those caused by Crohn’s disease, but the inflamed tissue generally appears only in the colon (the longest section of the large intestine) and the rectum (the chamber at the the end of the large intestine that stores the feces before it's eliminated). In ulcerative colitis the inflamed tissue is continuous instead of occurring in patches, and ulcers (sores) form on the lining of the large intestine. Only the surface layer of the intestinal lining is affected in ulcerative colitis, while in people with Crohn's disease the damage goes deeper into the lining.

Clostridium difficile is a bacterium that infects the large intestine, causing colitis (inflammation of the colon), severe diarrhea, nausea, vomiting, abdominal pain, dehydration and a fever. Infection by Clostridium difficile, also known as C. difficile or C. diff., may occasionally be fatal. This bacterium is classified as a superbug. Infections tend to develop in hospitals and other medical facilities, although they appear in the general community as well. Like other superbugs the bacterium is resistant to many antibiotics and is difficult to kill. In fact, the infection often appears in patients who have been taking antibiotics for a different reason. The antibiotics kill other bad bacteria and good bacteria as well, but don't affect C. diff. Without good bacteria to keep C. diff under control, the Clostridium difficile population increases and causes unpleasant effects.

In the large intestine, harmful microorganisms or a deficiency of certain helpful microbes may cause or contribute to intestinal diseases, and perhaps some other diseases as well. Fecal transplantation is an attempt to correct a health problem by improving the composition of the intestinal flora. The goal is to insert beneficial microoganisms into the large intestine, where they will hopefully reproduce, helping to create intestinal health and fighting or crowding out dangerous bacteria. Fecal transplantation is also known as fecal bacteriotherapy and human probiotic infusion.

Fecal transplantation is not a new technique. It’s been practiced for many years - even as early as 1958, as reported in the medical journal "Surgery", which describes some successful treatments by fecal transplantation. However, the process has only recently begun to be seriously investigated by researchers. Dr. Thomas Borody, an Australian gastroenterologist, is a leading practitioner of fecal transplants. He is not only treating gut disorders with fecal transplants but is also investigating whether other disorders such as multiple sclerosis, chronic fatigue syndrome and Parkinson's disease can be improved by fecal transplants. Other doctors are trying to find out if transplantation of beneficial bacteria from the stool of lean people into overweight people can treat obesity.

Fecal transplants are simple to perform and often have rapid benefits. However, the transplantation must be done by a doctor or under a doctor’s guidance. Donors and their feces need to be screened for known dangerous bacteria and parasites, or the recipient of the feces may develop a serious or even deadly infection.

At the moment, fecal transplantation is usually considered to be a “last resort” treatment for patients suffering from debilitating or very dangerous intestinal problems who have tried all other treatments without success. This is because there hasn’t been much scientific research concerning fecal transplantation (although this situation is changing now) and also because of the difficulty in ensuring that the donated feces is free of pathogens.

In Canada, the University Health Network, which contains three teaching hospitals linked to the University of Toronto, is recruiting patients for a controlled clinical study of the effects of fecal transplantation on certain intestinal diseases. This is the first such study in North America. If the results from this research and from other trials are favorable, fecal transplantation may become a mainstream medical treatment.