It has not been found in nature and no known organisms can digest or transport it.
Yet!
I often worry there's nothing microbes can't do with a little bit of mutation!
But what you're describing sounds like a quite valuable addition to our arsenal against drug-resistant bacteria. Is it possible we've finally found the way to stop them? Very interesting.
You're definitely right that bacteria can evolve to do almost anything so PNA degradation/interaction isn't out of the question once we start using PNAs to kill them.