Bacteriophages! Or Rock Beats Scissors and Viruses Beats Bacteria.
So say the superbugs win and we can no longer use any antibiotics we currently have. What next? One option is to have scientists develop newer, stronger antibiotics. Unfortunately, stronger antibiotics likely will end up causing more harm to the body, attacking more than just the offending bacterial cells.
If not antibiotics, then what? Scientists have started turning toward viruses to kill off bacteria. These specialized viruses, called bacteriophages, infect bacteria. Once in control, the phages use the bacterium's own internal machinery to replicate until the bacterial cell is full and then bursts like a balloon. The bonus of this therapy is that phages evolve along with the bacteria, making the problem of bacteria developing resistance to treatment easier to overcome. Another perk is that bacteriophages are very specific. They only target the particular bad bacteria you want to kill, and leave everything else, including other good bacteria, alone.
A derivative of this phage treatment with fewer complications for the patient is using only phage enzymes and not the whole virus. Bacteriophages produce enzymes called lysins that can eat through bacterial cell walls until they break open and fall apart, killing off the infection.
The idea of using viruses to combat bacteria was around before Alexander Fleming discovered penicillin, shuttling us into the era of antibiotics. Now that it looks like that era is ending, we're putting our money back on the viruses to help us fight off harmful bacteria.