Revisiting FMTs, and the patient that was cured of C. diff but became obese

Happy Valentine's Day to all our readers!  We will be back blogging on Tuesday, February 17, after we take off Monday, February 16 for President's Day.

Happy Valentine's Day to all our readers!  We will be back blogging on Tuesday, February 17, after we take off Monday, February 16 for President's Day.

Clostridia difficile infections can be nasty to deal with.  They cause pain and diarrhea, and are sometimes fatal.  They normally occur after a course of antibiotics, which leaves the gut in a state of dysbiosis where the C. diff can thrive.  Doctors normally prescribe antibiotics to cure this infection, but this can sometimes exacerbate the problem, making the gut even more prone to infection.  As we have discussed, fecal microbiome transplants (FMTs) have been successful in curing over 95% of C. diff infections.  Practically speaking, FMTs involve transferring the stool of a donor into the bowels of an infected patient.  While they are highly effective in treating C. diff, this practice is not without controversy.

The microbiome donor is generally a healthy person who is related to the patient and lives in the same household, generally a husband or wife.  The logic behind this is that these people share a similar microbiome, and some evidence supports this.  There are other ways to identify donors including the much publicized OpenBiome which has a stool repository which functions much like a blood or sperm bank.  These transplants come from ‘healthy’ strangers.  In most cases of FMTs, the stool is screened similarly to the way blood is screened, for specific diseases such as AIDS or hepatitis, and a few microbial pathogens (like C. diff).  The problem is, the microbiome is SO much more complex than blood, and as we learn every day on this blog, its impact on health and disease is not fully understood.  In fact, the promise of the microbiome is that it is connected with such far ranging diseases and phenotypes, from depression, to obesity, to arthritis.  We have numerous examples in mice where FMTs are actually able to transfer specific phenotypes, even unexpected ones such as anxiety.  What happens in humans though?  When we transplant feces between humans do phenotypes carry over?

Unfortunately, because the practice is mostly new, mostly unregulated, mostly isolated, and generally not a part of scientific studies, the long term impacts of FMTs are largely unknown.  The people who should and would know most about this, OpenBiome, have not published their findings, or at least are not talking about them.  We know that FMTs are really, really, good at curing C. diff, and may be the best solution to this debilitating disease, but at what cost is unknown, a classic bioethics dilemma.

Enter a healthy, 32 year old 136 pound woman from Rhode Island.  She had taken antibiotics for a vaginal infection and came down with a nasty C. diff infection which progressed over the course of a few months.  After antibiotics failed she opted for an FMT from her 16 year old, healthy daughter.  Fortunately, the FMT cleared the infection.  Unfortunately, over the ensuing year, the patient gained 34 pounds, and now weighs 170 pounds.  These are the kinds of results that make people nervous about FMTs.  We notice the weight gain because it is outward-facing and easy to measure, but what else has changed that we can’t notice, both physically and emotionally?  We need to be thinking about when we consider FMTs, especially when other, less complicated methods for treating C. diff are passing clinical trials.

FMTs exemplify both the promise and repercussions of the microbiome.  If the microbiome is as important and powerful as we think it is, then we need to investigate its clinical uses with deliberateness and care.

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The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.