Bacterial resistance can and has occurred via random genetic mutation which is the basis for evolution. As I say though, there is no reason why mutation can't go one step forward and two steps back. That is where I believe the theist component comes in.
I have to disagree with your statement on bacteria evolving using its resistance to an antibiotic. The end result is it is still a bacteria. Also I would like to add that mutation destroys information and does not add to. Things are not created out of chaos.