If we have enough drugs with different mechanics bacteria can’t out evolve all of them. It becomes less of a risk.
Ultimately resistance can evolve that kicks in only on exposure to the chemicals in question. Bacteria already do this with, say, the enzyme needed to metabolize lactose. The gene isn't expressed until lactose is present.
Kill it three different ways at once and it cannot adapt fast enough to leave dna fragments for the next microbe to pick up and continue the work.
AFAIK there is a new class of molecules specific to thwarting the resistance mechanism that makes the bacteria susceptible again in ways that cannot be out evolved. I'm looking for the general name for this technique - I do remember reading about it.