There are some situations where an organism can evolve overnight to exposure to an antibiotic. See Inducible Extended Beta lactamase resistance in E Coli. HOWEVER. Bacteria evolve just as any organism does via random genetic mutations that may or may not lead to resistance. It's Darwinism on the cellular level. The vast majority of antibiotic resistance occurred regardless of exposure. There is a segment of society that wants to blame humans for every problem it seems.