I think the problem with this kind of idea is that there are so many bacteria all over the world and you'll never reach all of them. Recall the very mechanism

I think the problem with this kind of idea is that there are so many bacteria all over the world and you'll never reach all of them. Recall the very mechanism that makes bacteria resistant over time: an antibiotic is deployed over a population of bacteria that have largely the same genotype but there are lots of mutations thrown in because they divide so fast. If any of the bacteria are resistant to the antibiotic, they survive and create a new population, again with largely the same genotype with lots of mutations thrown in, but this new population is entirely resistant to that antibiotic. Now you've probably been visualizing a human body or a petri dish when I talk about "a population of bacteria", but consider the entire Earth. You'll never deploy an antibiotic across all the nooks and crannies of the entire Earth, and even if you were to, you'd just get an ~evenly spread population of bacteria, resistant to that antibiotic. I guess you could _try_, if you were a supervillain or something.