> with cold fusion being further?

Cold fusion is in the realm of "impossible" with an asterisk of "kind-of possible but not the way people think" as muons can be used for fusion, but creating muons uses way more energy than the fusion they can create.

Cold fusion as in getting two regular atoms like H + H to fuse together without having mind-blowingly high pressure and/or heat is not possible.

Not neceserally: they still are in skin contact with the parents, and babies put EVERYTHING into their mouth, giving ample opportunities for microbes to start living in their guts.

Microbes are everywhere and our body has multiple "built-in" systems which help the good microbes to profalite. The gut microbiome is an ecosystem on its own, constantly changing and growing as our habits, environment, stress level, eating habits (and so much more) change while our immune system works hard to keep them in check and make sure they don't do anything which they shouldn't do.

> but don't work in the same way as the medications mentioned above.

I would say they DO work, but while antibiotics don't attack human cells (mostly, which is an important part) cleaning agents attacks everything indiscriminately. If you eat soap or drink bleach it does attack bacteria internally, but just as much your cells too.