Darwin's book was called "The Origin of Species". Antibiotic resistant bacteria are mutating and improving themselves, but are not becoming new species. So this phenomenon cannot be used to buttress evolution.
Evolution is simply the change in the frequencies of alleles from one generation to the next. The term evolution does not necessarily mean becoming a new species.
How can you tell when bacteria speciate? Define "species" as it applies to bacteria. Hint: the biological definition of species generally is accepted to be a group of organisms that can interbreed and produce fertile offspring. Bacteria reproduce asexually.