Be they variants that don't have the same properties that cause the nanogel to be attracted, or have cell walls that are too strong to be disrupted by the nano-stuctures, etc?
I guess my question is: are we talking about a 'final weapon' sort of thing, where any potential 'defense' would require ditching some attribute that makes bacteria feasible in the first place? Or are we just talking about a new weapon, one that we fully expect to eventually wane in effectiveness and thus will have to continue iterating upon?
Many of the papers raise that mechanism as a possibility, but they'll also note that there are many human cells that have a cell membrane at least as electronegative as bacteria, and that they witness antibacterial effects against relatively neutrally charged bacteria membranes as well. One example can be found here [1]. Try flipping through the mechanism and cytotoxicity (how dangerous it is to human cells) sections.
Basically, this is all exciting new research, but there really are no hard answers yet.
My interpretation is that the hyrdagel-based "nanomeds" have the main advantage that they break-up biofilm colonies, which have a higher (100-1000x) drug resistance than free floating bacteria. It seems to be operating through mechanical rather than biological methods, but the exact mechanisms aren't described well in either article.