You can remove the links from PR Web press releases, even after publication. No need to disavow unless they have been picked up by other sites and do-followed.
That said, I seriously doubt they can get you into trouble...unless they are part of a sustained pattern of misconduct, say dozens or hundreds of press releases from spammy press release sites (not PR Web, which is reputable.) Your backlinks from PR Web may even be helping.
There is much confusion on this subject. Two general and casual remarks Matt Cutts made years apart have been taken out of context and widely misinterpreted. The conventional wisdom seems to be that all backlinks from all press releases are always and everywhere useless or harmful.
This suffers from the defect of being untrue.
And it's s just as silly as saying:
"All directory listings are useless -- or harmful."
or
"All guest blogging is useless -- or harmful."
or
"All infogrpahics are useless -- or harmful."
Life is complicated. Context is everything.
And much depends on your overall link portfolio.