[neverdem]

Not true. Virii and bacteria cannot 'evolve' into drug-resistant strains because there is no such thing as evolution.

What do you call mutations that confer resistance to drugs in formerly sensitive organisms?

[ApplegateRanch]

What do you call mutations that confer resistance to drugs in formerly sensitive organisms?

In most cases, Natural Selection.

In the case of HIV, its Unnatural Selection.