Insects do it, rabbits and chimpanzees too; even your dog is at it. Many animals consume excrement in search of vital nutrients, like vitamins and minerals, as well as bacteria. Coprophagia, as this practice is called, is not very attractive for humans, but we have, however, been doing it for several years (although we haven’t been munching on poo, as such) and it’s saving lives. We’re talking about faecal microbiota transplants (FMT), a medical practice consisting in transferring in a controlled way faeces from a healthy person to another to treat a health condition. For instance, this practice has already been shown to be effective for treating the infection caused by Clostridium difficile.

One of the main problems with using this technique is the difficulty in isolating the bacterial strains from stools and getting effective concentrations. Now, a study carried out by researchers from the Spanish National Research Council (CSIC) and published in Scientific Reports shows a new technique that allows us to separate most of the gut microbiota from other faecal matter. Borja Sánchez, Ramón y Cajal researcher attached to the Dairy Institute of Asturias (IPLA), part of the food technology department at CSIC, is co-author of the research.


Where do we stand with regards to faecal microbiota transplants?

We’re at the very beginning. There are many conditions that include alterations in the relative compositions of the microorganisms that make up our gut microbiota. To ensure the technique is widely used, the effectiveness of FMT, or whether it is effective in some cases and not in others, should be verified. As, perhaps, we must also check if we just need to transplant certain bacteria or, on the other hand, whether there needs to be a drastic change in the profile of the microorganisms we have and see what the long-term effects may be.

In a society in which safety in all aspects of life are such a huge concern, knowing what a faecal microbiota transplant from another person can do to us in the long term is important. That is why one of the options currently being considered is the “autologous transplant”. Right now, I am well, I have a completely healthy gut microbiota and I keep a sample in case I need it in the future, for example, if I have to take antibiotics or have radiotherapy, so I could self-transplant my microbiota rather than someone else’s.

How is FMT carried out?

Either orally or rectally via a colonoscopy. In the former, there are several ways – from directly encapsulated stools to using a nasogastric tube to directly place a faecal suspension in the duodenum. The technique we have developed may help to improve how it is administered.

How does the new technique work?

It’s a simple process of gradient centrifugation, which does not affect the composition of the original microbial populations and which allows the component’s solutions to separate due to their density. The bacteria remain in a very specific section of the tube, which means we can quite simply ‘fish for them’. In 10 minutes you have your sample. We have also verified the effectiveness of the technique using metagenomic analysis of the microbial populations before and after extraction.

Why is this technique so important?

Because it is a simple strategy for obtaining representative gut microbiota from faecal samples. On the one hand, we can design a protocol that will guarantee the viability of the bacteria, as they are highly sensitive to oxygen. And on the other, we can obtain bacterial concentrations – with 2g of stools and this methodology, we can obtain up to 1010 bacteria. This way, if we want to provide an individual with treatment using encapsulated stools, whereas they now require at least ten tablets to get an effective dose, if we manage to concentrate the microbiota, perhaps they will only need one.

Where did the idea for developing a technique of this kind come from?

It came from a study that we were carrying out on gut microbiota in patients with systemic lupus erythematosus (SLE), an autoimmune disease. We wanted to analyse faecal matter, but between 40% and 50% of stool content was of no interest to us and it interfered with our research. So we tried to see if, through a simple process, we could separate faecal microbiota from the rest of the stools’ components. And we succeeded.



Arancha Hevia, Susana Delgado, Borja Sánchez et al. Application of density gradient for the isolation of the fecal microbial stool component and the potential use thereof. Scientific Reports. Doi: 10.1038/srep16807