Fresh or frozen…which is best?

Faecal Microbiota Transplant may be performed using either fresh or frozen stool. Some people in the field have suggested that fresh is the ideal, however, at Taymount we are very particular about the material we use, and the safety of our patients is our highest priority.

We never use FRESH material, ever.  In the 1980s, the whole world became aware of possible HIV transmission through contaminated blood products some years ago.  If we learned anything from this sad episode, we learned that we must not pass unscreened or inadequately-screened body fluids from one person to another.  The argument that the donors are fully screened and tested when using fresh, is a faulty one, for the reason that there are several serious disease conditions which do not show up in blood or stool tests for several weeks whilst incubating; during this incubation or latent period, many transmissions and cross-infections can occur.

  1. HIV – this disease can take up to 12 weeks to register in a blood test. Negative test results obtained during this time cannot relied upon as being safe or accurate to go ahead and transfer stool.
  2. Hepatitis A, B, C – these diseases can also take up to 12 weeks to register in blood tests. Once again, any negative test results are not comprehensive and cannot be relied upon as indicating that the material is safe to transfer.

Taymount clinic will screen donors for such diseases in addition to the list of diseases commonly felt to be necessary to screen for, but we will store the material obtained for 3-6 months and only release it for use once sufficient subsequent blood tests can prove the 12-week period after each donation is free of disease.

In addition to the safety aspect, there are many other advantages to using frozen material.

It can be stored and defrosted as required, which allows for flexibility of use and means that our patients aren’t left waiting for a donor to ‘perform’ on the spot!  It also means that the samples can be shipped in cryo-protective packaging.  Patients are able to take home additional implants and can order more in the future should they need them after a round of essential antibiotics, or a bout of food poisoning.

The freezing of bacteria isn’t a new development and there are many other instances where this is performed safely and successfully with no damage to the bacteria themselves. Contaminated food still harbours the same harmful bacteria even after freezing; organs and blood are frozen for transplants with no adverse effects; women’s eggs and men’s sperm are frozen to preserve their fertility; and even human embryos are still viable after being frozen for considerable periods, sometimes even for years.

There is also no need to worry that frozen implants won’t be as beneficial as fresh; in fact a 2016 study comparing fresh and frozen stool in patients with C. difficile found that frozen stool was just as efficacious as fresh.  A meta-analysis in 2017 also observed that in patients with refractory or recurrent C. difficile, frozen FMT was just as effective; and a 2014 study followed up on patients 1 year post FMT and found that the success rate was 88% for both fresh and frozen stool.

Patients at Taymount can rest assured that their FMT implants have been carefully processed, frozen and quarantined, so that they are both safe and effective.

Enid Taylor
ND, BSc (Hons) Psych
Clinic Director, Taymount Clinic

Nina Mansell
Nutritional Therapist


  1. Lee, C. Steiner, T. Petrof, E. Smieja, M. Roscoe, D. Nematallah, A. Weese, J. Collins, S.
  2. Moayyedi, P., Crowther, M. Ropeleski, M., Jayaratne, P., Higgins, D. Li, Y. Rau, N. Kim, P. (2016). Frozen vs Fresh Fecal Microbiota Transplantation and Clinical Resolution of Diarrhea in Patients with Recurrent Clostridium difficile Infection. JAMA, 315(2), p.142.
  3. Tang, G. Yin, W. Liu, W. (2017). Is frozen microbiota transplantation as effective as fresh fecal microbiota transplantation in patients with recurrent or refractory Clostridium difficile infection: A meta-analysis? Diagnostic Microbiology and Infectious Disease, 88(4), pp.322-329.
  4. Satokari, R. Mattila, E. Kainulainen, V.  Arkkila, P. (2014). Simple faecal preparation and efficacy of frozen inoculum in faecal microbiota transplantation for recurrent Clostridium difficile infection – an observational cohort study. Alimentary Pharmacology & Therapeutics, 41(1), pp.46-53.