The digestive system is supposed to be fully sandboxed from the host. Topologically it is as exoneous to your body as your skin and the sandboxing is necessary for your bacteria to not digest yourself.
I would appreciate references on permeability mechanisms allowing for bacteria movement inside the body, on healthly humans.
I mean there is a digestive system to human blood interface but I doubt it allow bacteria/archae/parasites/shrooms/atypical single celled eukaryotes to cross it.
(little known but ~30% of your microbes are not bacteria but archae and withouth those we would not fart)