Most antibiotics and antibacterial agents work by retarding the reproduction of bacteria rather than outright killing them. Those that do actually kill them often do so by hindering cell division without hindering cell growth, causing their membranes to burst once the cell reaches too great a size to stay contained. Bacteria that acquire resistance to such agents are those that modify their process of cell division so that they are less dependent on whatever process the antibiotic inhibits. This makes them better suited to their current environment, but actually makes them less suited for their previous environment. Resistant bacteria never reproduce as quickly as their mother strains in the absence of the chemicals that favor their development. If you don't have access to antibiotics anyway, then antibiotic resistant strains of bacteria are actually much less dangerous than the strains from which they mutated.
Of course, most antibiotic an antibacterial agents do not effect only dangerous bacteria, but also the helpful kind. Not having enough good bacteria is often a bigger problem than having antibiotic resistant bad bacteria.
These days some of the most promising research into how to stop or prevent bacterial infections does not involve killing them or inhibiting their ability to reproduce, but rather tricking them into thinking there is no room to grow. Bacteria all produce and detect certain chemical markers to to help in in Quorum Sensing, their ability to determine how many other bacteria are also present in their environment and whether or not they are of the same kind. This warns them not to overproduce when they are approaching their environment's carrying capacity. There is apparently one such substance that is used by all bacteria, and various others produced by different strains. Having large amounts of harmless bacteria producing quorum signaling substances tell both harmful and helpful bacteria that there is little or no room for growth. We could also produce this substance artificially and use it to make bacteria think that a sterile surface is already overpopulated. To be really useful though, we ought to identify and reproduce the quorum signaling chemicals used by harmful bacteria, so that we can make pathogens act as if there are too many of them and deactivate their trigger to reproduce while not inhibiting the growth of those with whom we share a mutually beneficial symbiosis.
But, yeah, let's talk about that elsewhere if we're gonna.
