When Fleming discovered the first natural product antibiotic Penicillin in 1928, the discovery was groundbreaking for medicine. Antibiotics were a tool with brute force. Without knowing details about the illness from which a patient was suffering antibiotics allowed a doctor to fight illnesses due to bacteria.
Penicillin proved to be very useful for preventing wounds in the second World War from getting infected and research went into scaling up the production of it. After the war it came to be called a wonder drug. Economically, the fact that one antibiotica can be used for many different illnesses made it in the middle of the 20st century very profitable to patent new antibiotics and bring them to market.
With antibiotics usage in full force phage therapy that was used a bit within the 1920s and 1930s stopped being used in the West. Phage therapy had the problem of being a solution that only targeted very specific bacterial species and sometimes only specific strains of bacteria. Frequently, phage therapy failed because it was not targeted towards the bacteria strain with which a patient was infected.
While Western health authorities managed to get a framework that allows new flu vaccines to be approved in a short time frame to react to a changing virus, we lack a regulatory system that allows new phage cocktails that are needed to deal with evolving bacteria to be approved without going through multiple years of clinical trials.
The property of being a very specific treatment has the drawback that it's necessary to test the patient, to know which bacteria infects the patient, to be able to choose the right treatment. In the past it was both expensive and time consuming to test for the bacteria that causes an infection.
In Poland there's the Phage Therapy Unit which provides Phage therapy for chronic drug-resistant bacterial infections but they operate under an exception for experimental procedures. They published a review titled Facing Antibiotic Resistance: Staphylococcus aureus Phages as a Medical Tool about using phage therapy for treating staphylococcus and argue in another paper that their way of treating patients might be more cost-effective than conventional treatment with antibiotics.
The cost of providing medical treatment matters a lot and causes our health care systems to spend more and more money. DNA sequencing is the one central technology that fell a lot in price in the last decades and while it doesn't fall faster than Moore's law anymore there is still hope that continued progress will allow it to be cheaper in the future. Whole-Genome Sequencing (WGS) can not only be used to sequence human DNA but can also be used to sequence bacteria DNA of infections. In several countries WGS-based pathogen typing is already in the trial phase for implementation as a routine tool for the monitoring and detection of multidrug-resistant bacteria pathogens.
As this sequencing becomes common place, doctors will have the relevant data to target specific strains in their patients with phage therapy. I predict that there will be a multi-billion dollar company that uses machine learning to pick the right phage cocktail to treat an infection based on the results from WGS-based pathogen typing.
Phage therapy will get around antibiotic resistance and it will only kill harmful bacteria, while not killing friendly bacteria the way antibiotics do. A company that uses machine learning to iterate on their phage cocktails will give us a more effective alternative to antibiotics.