We know that mutations happen regularly in bacteria and also that one bacteria might get the mutation and become stronger than the others and thus survive, causing antibiotic resistance as well. Can we deliberately make mutations in bacteria that would harm other bacteria but not humans. This would not only make them stronger and thus let them survive but would reduce the very need of antibiotics as they would be less virulent to humans?
Mutating Bacteria is a very plausible idea. If you mutate a particular strain of 'helpful' bacteria to become extremely positively selected for in the current environment then it is possible that the rest of the bacteria interacting with your new mutated will face heavy competition and eventually die out.
The major hole in the idea however, is that bacteria regularly undergo horizontal gene transfer which makes this idea extremely, extremely dangerous for humans. (If your mutated bacteria accidentally passes on the mutated gene to, say, a bacteria that causes Tuberculosis, it would initiate a pandemic. It is also equally possible that a dangerous bacteria might transfer its genes to your mutated bacteria.) It is generally accepted that mutating bacteria or other pathogens(most of which mutate at high rates) is generally a bad idea, because once released into the environment, the possibilities of the mutation going haywire are high(other mutations might make them dangerous).
Horizontal Gene Transfer: Transfer of genes due to recombination processes like Transduction, Transformation and Conjugation which can occur between bacteria of same or different strains, species, domains. etc