First: the evolution of microbes you reference is microevolution. It is clearly observable; both in nature and in the laboratory. The Darwinian theory of evolution from one species to another, macroevolution, has never been observed. (Microbes don't evolve into nematodes) Macroevolution requires some logical leaps of faith that are at least as great as believing in a Creator. Search the evidence and you will see where the logical gaps are.
Secondly: there are many antibiotics that have been around for more than 40 years that are still effective today.