My guess is, you rarely stop to consider the contents of your feces. That’s fine. I’m the sort of person that talks about fecal transplants at dinner parties, but I don’t expect everyone to be excited about it. 

But really, fecal transplants are AMAZING! It’s exactly what it sounds like - you take the poo from a donor, and give it to a recipient. This is probably the easiest organ donation ever - as a donor, you’re hardly put out at all (turns out you can make more), and the transplant is pretty straightforward - you can actually go two ways: a tube down the throat or up the bum. But why? 

This procedure is shockingly effective at treating a pretty horrible gut infection by a microbe called Clostridium difficile, which can be a normal part of your gut microbiome, but can grow out of control when the rest of the bacteria in your gut get thrown out of whack. The trouble is, C. diff (as it’s commonly known) is more resistant to antibiotics than the other bugs in your gut, so you can’t really use antibiotics to treat it (they kind of make it worse).

The idea in this case is to re-set the microbiome back to a healthy state by introducing a healthy microbiome. And it works! Some scientists are also looking at using fecal transplants for other health conditions like inflammatory bowel disease and even obesity. Companies like Ceres Therapeutics are trying to develop treatments bacteria-in-a-pill treatments for C diff to remove the variability (and frankly the ick-factor) around fecal transplants. It’s all about the microbes being transferred…

… or is it?

Fecal Transplants: What Is Being Transferred?

An article published last month in PLoS Biology asks this question. It turns out that there’s a lot of other crap in your crap other than bacteria, and many of them could plausibly have a biological effect. 

The vast majority of solid matter is organic material, whose makeup consists of 25%–54% microbial cells (with a slight portion likely consisting of viruses) that may be alive or dead [18]. As microbial counts were based on light microscopy and a modification of the Gram stain, the microbial cells were presumed to be mostly bacteria [18], but quality evidence is lacking. Several other components are found in significant concentration, including archaea, fungi, and microbial eukaryotes.

The paper is open access and well worth reading. Frankly, it had never occurred to me if the rest of the contents of feces were playing a role. But this question is critically important as scientists and physicians consider developing therapies on the microbes in the gut.

Just recently, a clinical trial for SER-109, the pill being developed by Ceres, completely bombed. This might be because they didn’t have the right cocktail of bugs, but could it also be because of some of these other components in stool? Very possibly.