It's called adaption, not evolution. They're both two different things. An organism evolving from say, for example, a monkey into a human is way different then a bacterial strand adapting to the medicines we have so it can survive.
Adaptation is a HUGE component in the theory of evolution. Adaptation is synonymous with micro-evolution. (Plus keep in mind that a recent test has determined that chimps are 95% genetically identical to humans. So not that many changes would be needed, really. Australopithecus, anyone?)