Before or after DNA mapping? Further, if macro-evolution were a reality, odds are getting better all the time that one of those experiments will yield a multi-celled organism (the "holy grail" of macro-evolution). I will say that the fact that it hasn't happened yet is not proof against macro-evolution; just that the probability for it is lacking.
I don't care whether you use DNA data or not, how do you know that the antibiotic resistant bacteria present after treatment with antibiotic are not a different species from those that you start with. My point is that the whole macro vs micro question is irrelevant because species is a human defined concept. Treating the idea of "species" as some fundamental concept is problematic at best. Defining species as being a group of organisms that can interbreed (which would be a fundamental concept) leads to problems. For example, it doesn't help us in the bacteria example. Additionally, the ability to interbreed is not transitive whereas the classification of organisms into species is. That is, if A is the same species as B and B is the same species as C, then it follows logically that A and C are the same species. However, it is possible for A and B to be capable of interbreeding and for B and C to be capable of interbreeding but A and C to be incapable of interbreeding. If that's our idea of species, then are A and C the same species or not? If you use similarity of anatomical features, you are imposing a human defined classification scheme on the idea. No two organisms are identical. It requires a subjective choice to determine that variation X is a different species and variation Y is a simply a variant within a species. That's why DNA mapping won't help. No two bacteria have exactly the same DNA sequence. How much variation would be needed to conclude that a new species has formed?