Antibiotic resistant bacteria are a growing threat, causing deadly infections that cannot be cured by our standard antibiotics. The development of antibiotic resistant bacteria may be further fueled by strained resources, increased hospitalizations, and decreased surveillance during the SARS-CoV-2 pandemic. 

With limited development of new drugs to treat resistant bacterial infections, new therapies are desperately needed to prevent the spread of these “superbugs”. To this end, researchers are looking to a natural predator of bacteria – bacteriophages. Bacteriophages or “phages” are viruses that specifically infect bacterial cells. Depending on the type of phage, this infection can ultimately kill the bacteria that usually resist antibiotic treatment. Though commercial therapies are not yet available, the use of phage therapy is a hot topic boasting thousands of studies and several famous success stories.

While phage therapy shows great promise in the fight against resistant bacteria, these superbugs are constantly adapting and can evolve quickly to even resist phage infections. Fortunately for us, this resistance often comes with a cost. Researchers at Monash University have found a way to leverage the trade-off made by a phage resistant bacteria to make it once again susceptible to antibiotics. 

Antibiotic-resistant Acinetobacter baumannii (A. baumannii) is considered an “urgent threat” by the Centers for Disease Control and Prevention. Like many disease-causing bacteria, A. baumannii forms a sugary outer capsule that can protect the bacterial cell from antibiotics and make it deadlier. However, the researchers behind this new study discovered that A. baumannii's protective layer also serves as the entry point for phage. 

When the team exposed different strains of A. baumannii to phages in the lab, the bacteria quickly developed phage resistance by shedding their outer capsule to lock out the viral invaders. While capsule-less bacteria were protected from phage infection, researchers found that the mutated strains of A. baumannii were also re-sensitized to several antibiotics. Through experiments where they infected mice with A. baumannii, they also discovered that decreased bacterial reproduction in a host is another trade-off for phage resistance. They concluded that phage therapy can be effective in treating this superbug infection. 

The CDC notes that infections from A. baumannii most often occur in healthcare settings, and people at highest risk are those who are on breathing machines (ventilators), in intensive care units, or have prolonged hospital stays. With these situations currently all too common in hospitals full of COVID-19 patients, phage therapy may provide an option where other treatments fail.