Oh. So how do pathogens change to enable them to tolerate antibiotics? Maybe the Designer reaches in and changes that DNA? You do realize we can sequence DNA and show where these mutations have occurred, don't you?
Pathogens (Virus types) sometimes use a process known as "antigenic drift" which enables them to connect with mutations where antibodies bind and they are then able to reinfect hosts which would be immune but are not because the specific antibodies are in fact specific.
That is not evolution. That is microbes (sub microbes, whatever) changing outfits every now and then in order to get into a club that they have been permanently kicked out of. I wish that I were not so tired, it were not so late here, and that I really was interested in beating all the time out here on this dead horse.
And, you have been reading too many X-Men comic books if you are of the mind that "mutations" are a positive thing among biological creatures. Mutations are defective offspring.