[Sofa King]

"Well, if natural selection can describe any given genetic state, of any given population of organisms,"

It can't. Natural Selection would be at a loss to describe a species developing a trait that made it less likely that the members of the population who possesed it would be able to survive, breed, and pass on their genes (although the we may not always understand what the advantage of a given trait is).

If, for example, a culture of bacteria was routinely exposed to an antibiotic that it was previously immune to, it would be a violation of natural selection if that culture's future generations slowly started becoming susceptible to it's effects.

[csense]

Natural Selection would be at a loss to describe a species developing a trait that made it less likely that the members of the population who possesed it would be able to survive, breed, and pass on their genes.

No offense, but you're not making any sense here. If a species or population develops a trait ( via survival, breeding, inheritance) then in what way have they not survived, bred, or passed on their genes...including trait X.

As your statement stands, I don't think a logical contradiction is evidence of an observation that in principle could falsify natural selection.

If, for example, a culture of bacteria was routinely exposed to an antibiotic that it was previously immune to, it would be a violation of natural selection if that culture's future generations slowly started becoming susceptible to it's effects

Again, you're not making any sense.

It's not a violation of natural selection if an organism, or group of organisms, fail to inherit any given trait, beneficial or otherwise...and if they did inherit the trait, and it's dominant, then you have another logical contradiction on your hands. The only other alternative is that the trait is recessive, which again, is not a violation of natural selection