My dermatologist prescribed handfuls of tetracycline to battle my teenage acne. I took around 8 pills of the stuff daily for years. My GI tracks been messed up for years and there was very little improvement in my acne.
There is also promising things happening with fecal transplants (FMT) I am told.
Every time I take antibiotics I run 60% chance of a fungal infection somewhere, so I have my own regimen to keep that annoyance away.