It would be nice to see some positive examples of where species (GM or otherwise) have been artificially introduced to an ecosystem and not ended up doing more

It would be nice to see some positive examples of where species (GM or otherwise) have been artificially introduced to an ecosystem and not ended up doing more harm than good. Otherwise, this kind of thing makes me sceptical, as there are always unintended consequences. I would only use this treatment if (amongst other things) the strain was engineered to be very sensitive to a very specific narrow-spectrum antibiotic, that is NOT produced by the same company offering the bacterial strain.