essentially like nanobots to fix things in a human body, but biological ones. OK so far...
But what happens if the human immune system sees them as an infection when they are used as a treatment? I assume injecting them as part of a treatment, like little cancer eaters or something. Or maybe they just STAY in the lab and make designer drugs?
E-coli from other organisms (than yourself) can play havoc on your health. best not let this get out (like OTHER "things": that have been demonstrated to escape from a lab and cause WORLDWIDE HAVOC)