Time to stimulate research into phage therapy instead of granting longer patents to antibiotics. The field seems promising with a long history in Russia but mostly ignored in the west until recently. https://en.m.wikipedia.org/wiki/Phage_therapy
Phage therapy is neat, it really is, but there are a couple major issues:
- There is no such thing as a "broad spectrum" phage. You can't do empirical treatment using phages, and there's not really "off the shelf" phage therapy - it tends to be a bespoke creation for a particular infection.
- There's some serious regulatory problems, similar to those experienced by fecal transplant treatments. We're not yet really equipped to think about handling evolving, custom microbes as a treatment. - Because of the first, it's going to require a considerable amount more lab capacity than most clinical settings currently have, and considerable delays until treatment.
- There's also some biosafety issues around phage prep, but those are easily solvable. It's a great way to treat particularly resistant or hard to treat infections, but it's not a particularly great general solution. There's a reason it was abandoned in countries with easy access to antibiotics - they're just roundly superior in basically every respect.
You are right that phage therapy is very challenging under current regulations. If we want phage treatments we are going to need to change how drugs are licensed.
The basic idea is really simple. Phages come as both generalists and specialists (and all grades in between). The specialists grow on a limited range of bacterial strains, while the generalists can grow on a wide range of bacteria (even different genera). The specialist phages grow faster than the generalists in a single bacterial strain as they are better adapted to their specific host. The problem is that when most groups isolate phages from the environment they only use one bacterial strain at a time so they end up isolating specialists rather than the generalists; the generalists are just too slow to form visible plaques in the presence of specialists.
The solution to isolating broad host range phages is to use multiple bacterial strains in the enrichment and isolation process (we used up to 50 at a time). Under these conditions the generalists grow faster since they have more hosts they can infect (i.e. the specialist can only reproduce in one bacterial strain, while the generalists can reproduce in multiple). This tips the isolation process towards pulling out generalists phages that have a broad host range. I have to say when I entered the field I thought that this was the way everyone isolated phages as it is so obvious, but I was wrong.
The "drug" keeps changing. The neat part of phage is that they co-evolve along with the bacteria they're feeding on, but it means there's no really consistent formulation. It's unique, and it's not fixed.
The same problem effects fecal transplant. "The healthy gut flora of a donor" is much harder to approve and regulate than "Famotidine 10mg, Calcium carbonate 800 mg, Magnesium hydroxide 165mg" (the antacids on my desk).
It'd be a tool, but not a broad solution.