I used to make kefir but lately I've been into homemade sauerkraut, either one is loaded with good bacteria.
Supposedly your appendix (assuming you still have one) is the body's reserve of good bacteria for those times when your system flushes things out, like during dysentery season or whatever other nasty stuff nature tossed our way. Not sure if modern anti-biotics (like doxycycline and it's ilk) destroy the bacteria in the appendix also. Wouldn't be surprised if they did.
But anyway, when I'm taking Humaworm I still eat sauerkraut and used to drink kefir. "It couldn't hoyt!"