I read this interesting article online about how deadly bacteria are known to attack other deadly strains of bacteria. https://www.google.com.sg/amp/s/phys.org/news/2013-02-deadly-bacteria-remarkable-precision.amp I am wondering how normal bacteria that infect us like those that cause strep throat and so on also have the capabilities to attack other bacteria and how feasible it is to use this as a treatment for bacteria infections by introducing harmless strains od bacteria to fight pathogenic versions (maybe like probiotics?)
Mixed bacterial populations, where not engaged in some kind of mutual or commensalistic relationship, are constantly at each others throats over resources. Even then, sometimes it's just rate of growth isn't terribly bad for each commensal. Not just nutrients, for example, but also precious space to colonize or attach to. There's a good review here, and among some of the tactics direct killing by antimicrobial production is an option. You also have other factors, however, such as secretion of molecules that impair attachment or quorum sensing. Also, virulence factors that give a competitive edge such as evading immunosurveillance (encapsulated B. anthracis strains vs unencapsulated, for example).
So here's the hard part: you want to engineer an attenuated bacterium that goes in and attacks a pathogenic strain. While I'm sure possible, you would certainly need to ensure that what you take away to attenuate your strain doesn't gimp it in vivo. You also need to realize that your target pathogen is very capable of simply "changing" itself to avoid dying to the engineered strain. Once your mechanism of action has been defeated, your product has been defeated. I think that it's fundamentally different from commercial virus-based products like T-VEC, as well, due to the level of variability.
One of my thoughts is your strain needs to be able to compete with the pathogen in the first place to stand a chance, which may be difficult if you cut out too many virulence factors trying to make it "safe."