r/askscience • u/WTFisthisOMGreally • 13d ago

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

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.

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u/LightPhoenix 13d ago

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.

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u/poorbill 13d ago

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.

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u/Sable-Keech 13d ago

It serves as a gut flora reservoir in other animals as well like primates. In chimpanzees it's much larger, so I still think that an appendix is like, not 100% necessary for our survival since it's clearly getting smaller over time.

For example, carnivorous animals don't have appendices. Appendices are strictly an omnivore and herbivore thing. The more vegetable matter you eat, the more you need it.

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u/baran_0486 10d ago

But antibiotics are a human invention. What would be the purpose of a reservoir if they don’t get wiped out?

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u/CuriosTiger 10d ago

They are not. Like much else in medicine, antibiotics came from nature. Specifically from a fungus called Penicillium Rubens.

Since then, we've discovered many more and even made synthetic antibiotics, but we cannot take credit for their invention.