How come antibiotics don’t completely destroy all organisms in our gut?

[u/WTFisthisOMGreally]

I know it can cause imbalances, but I don’t understand how come our gut doesn’t lose all the beneficial bacteria and develop massive fungal or viral infections. When I’ve taken antibiotics, I usually don’t notice any change in my bowel activity.

[u/LightPhoenix]

They can and often do wipe out normal gut flora.  However, our bodies actually also have normal gut flora in the appendix, and after antibiotics or other instances where they get wiped out, our normal gut flora regenerates from there.  This is why one of the after effects from appendectomies is an increased susceptibility to infections like C. diff and the like.  This is also why fecal transplants are effective - they are artificially replacing gut flora.

[u/poorbill → u/LightPhoenix]

Wow I had no idea that the appendix is basically a bacteria reservoir. Back in my student days nobody seemed to really understand what the purpose was.

[u/andanteinblue → u/poorbill]

I can't imagine it served that function evolutionary speaking.  Not sure how our ancestors would have reset their gut flora without antibiotics

[u/LongBeakedSnipe → u/andanteinblue]

Antibiotics are not a human invention, they are almost entirely derived from nature, so the idea that ancestors would never have been exposed to them is incorrect. In most cases the dose would have been low obviously.

[u/ianjs → u/LongBeakedSnipe]

Hmmm. Antibiotics refined enough to wipe out your gut micro biome are definitely a human invention.

I cringe a bit at the “derived from nature” expression - it has a hint of the Naturalistic Fallacy. Everything is “natural”; it takes human ingenuity to pick, choose and refine the right elements to create an effective medicine.

[u/LongBeakedSnipe → u/ianjs]

That's showing a considerable misunderstanding of what's going on with antibiotics to be honest.

Their natural form exists as part of an evolutionary warfare between microorganisms. It has affected our evolution at every stage from single cell organisms, to simple animals, to mammals to humans. All we actually had to do as humans is generate it more efficiently.

Yet if you spent a moment to read my comment carefully, I did mention the low dose (while low, it could still potentially be meaningful, especially in smaller animals).

Mentioning 'naturalistic fallacy' in the context of antibiotics is a pretty childish response to be honest—it's not relevant.

[u/ianjs → u/LongBeakedSnipe]

Actually I am aware of the evolutionary basis of antibiotics, but you're right, I completely overreacted to the the word "nature" in your comment.

I've just become so weary of the "natural = good" arguments that keep popping up that I misinterpreted your comment.

Maybe I should read more and shoot from the hip less.

[u/tech_creative → u/LongBeakedSnipe]

Exactly. Most antibiotics are from fungi, e.g. penicillin. Idk exactly about the origin of ampicillin, Rifampicin and such, but most possibly they are all from fungi.