Why are bacteria more likely to colonize when doing FMT compared to taking regular probiotics?

It's because they are FROM a human gut, so they are already selected for being able to survive there! SOME of the probiotic species (such as Lactobacillus acidophilus) were originally isolated from stool, but none of them have been cultivated in the gut for many, many generations.

In addition, FMT contains MANY more species than probiotics. The most diverse of regular probiotics have 20-30 species (most contain <10, and some really rare probiotics, particularly Equilibrium, have >100, albeit none of them isolated from the gut), whereas FMT contains hundreds or even thousands. The majority of species even from a FMT don't colonize long-term, but when you have hundreds of them in total, the chance that at least a few species DO colonize is very high.
 
It's because they are FROM a human gut, so they are already selected for being able to survive there! SOME of the probiotic species (such as Lactobacillus acidophilus) were originally isolated from stool, but none of them have been cultivated in the gut for many, many generations.

In addition, FMT contains MANY more species than probiotics. The most diverse of regular probiotics have 20-30 species (most contain <10, and some really rare probiotics, particularly Equilibrium, have >100, albeit none of them isolated from the gut), whereas FMT contains hundreds or even thousands. The majority of species even from a FMT don't colonize long-term, but when you have hundreds of them in total, the chance that at least a few species DO colonize is very high.
Thanks! This was a very helpful and well thought out reply! I appreciate it!
 
Synergy and CFU play a major role. An FMT will contain microbes that assist each other in survival and will number in the trillions, rather than billions (like most probiotic supplements). It also helps if the FMT is performed using a stool sample that had just recently exited a person (e.g. within 15 minutes). The more the stool sample is processed, the less effective it is likely to be. Not to mention that the stool itself can act as a buffer.
 
The more the stool sample is processed, the less effective it is likely to be.
My own experience and the experience of people I have read about (patient testimonials as well as comparing across clinical studies), this is NOT true. In fact if anything the opposite is true, where patients had good experiences with stool banks/providers who process more extensively and struggle to reproduce that with providers who don't, or studies that used more processed stool reporting a higher percentage of successful FMTs than studies that used less processed stool.

Of the people I have encountered who advocate using minimally processed stool, I don't recall seeing ONE who has actually had the chance to try both highly processed and minimally processed FMTs and who reported a significant difference in response in favor of the minimally processed FMT (if you know of one, please do share it here). The only people I see arguing in favor of minimally processed stool are either those who have never actually done a FMT at all, or else have ONLY ever used minimally processed stool, and who are therefore speaking from assumption and/or educated guessing, not from actually having ever experienced firsthand a worse result from highly processed FMTs (or from knowing a friend or acquaintance who did).
 
My own experience and the experience of people I have read about (patient testimonials as well as comparing across clinical studies), this is NOT true. In fact if anything the opposite is true
Don't you have a science degree? You constantly say the most unscientific things, demonstrating a fundamental lack of understanding of how basic evidence works.

Overwhelmingly, the evidence contradicts your claims: https://humanmicrobiome.info/where-to-get-fmt/

The sources that process their stool (Openbiome, Taymount, etc.) have had the worst results by far. And the source that doesn't process it at all (Human Microbes) has had the best results, by far, and would be even better if I did not allow people to choose lower-ranked donors.

One can also browse through the studies that got poor results and see that they processed the stool:


Your personal anecdote does not overrule all the other evidence.

Overall, processing of the stool seems largely irrelevant. Donor quality is really the only factor that seems worth worrying about.

studies that used more processed stool reporting a higher percentage of successful FMTs than studies that used less processed stool
I think you just completely fabricated this claim to support what you want to be true. Go ahead and look through the studies I referenced above, and make a thread here listing their processing: https://forum.humanmicrobiome.info/forums/fecal-microbiota-transplant-fmt/?prefix_id=63

Of the people I have encountered who advocate using minimally processed stool, I don't recall seeing ONE who has actually had the chance to try both highly processed and minimally processed FMTs and who reported a significant difference in response in favor of the minimally processed FMT
This is not how scientific evidence works. Anecdotes are ranked very low on the Hierarchy of evidence.
 
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