New virus treatment eliminates drug-resistant superbugs

The Fight Against Antibiotic-Resistant Germs

In one of the most active hospitals in Melbourne, a dangerous outbreak of antibiotic-resistant germs forced doctors and researchers to seek new ways to combat the threat. The main culprit was the Enterobacter cloacae complex (ECC), a group of bacteria known for its ability to resist nearly all antibiotics. When ECC infects patients, it often leads to severe bloodstream infections that can be life-threatening.

To tackle this issue, scientists from Monash University and The Alfred Hospital turned to an old but promising solution: bacteriophages, or phages. These are viruses that specifically target and destroy bacteria. Their research led to the development of Entelli-02, a therapy composed of five carefully selected phages designed to fight the exact strains of ECC found in their hospital.

This breakthrough represents a significant step forward, as it provides doctors with a treatment tailored to the specific bacteria they encounter in their own institutions.

Why Phages Matter

Phages are unique because they can precisely target certain types of bacteria without harming others. They work by injecting their genetic material into bacterial cells, which then replicate and eventually burst the host cell open. This specificity is both an advantage and a challenge—while it allows phages to eliminate harmful microbes without affecting beneficial ones, it also means that a phage effective in a lab may not work against a patient's infection.

ECC belongs to the ESKAPE group of pathogens, which are notorious for escaping the effects of antibiotics. These bacteria pose a growing global health threat, with Enterobacter infections alone causing over 200,000 deaths worldwide in 2019. Hospitals like The Alfred have been at the forefront of efforts to combat these resistant microbes.

The Development Process

The research team started with 206 bacterial isolates collected over ten years. From these, they selected 36 that represented the genetic diversity of the collection. They tested 21 different phages and found that almost every bacterial strain was susceptible to at least one. They then created a preliminary cocktail, called cocktail-V1, using three of the most effective phages.

While this early version showed promise in laboratory and animal tests, it wasn't enough. When tested against a wider range of bacterial strains, its effectiveness dropped significantly. Only about half of the hospital isolates were eliminated, with some strains like ST114 and ST190 showing resistance.

Training and Recruiting New Phages

To address this, the scientists used two strategies. First, they "trained" some of their phages by exposing them to resistant bacteria, which led to improved infection capabilities. Within a week, many of these phages became much more effective, sometimes increasing their killing potential by thousands of times. Genetic analysis revealed that these improvements occurred in the viral tail fibers, which help phages attach to bacteria.

Second, they searched for new phages that could target the resistant strains. Two new candidates, øNando and øTaquito, proved to be valuable additions. Both could survive long-term storage and effectively killed even the most resistant bacteria.

With three modified and two new phages, the team had five options to test in the next phase of development.

The Final Mix: Entelli-02

After trying various combinations, one stood out. Using the improved versions of the original three phages and the two newcomers, the final mix, named Entelli-02, was able to infect nearly 88% of the hospital’s bacterial collection. In test spot trials, it killed 92% of the isolates, a major improvement over the initial attempt.

Entelli-02 was produced under strict human-use conditions at the Monash Phage Foundry. Each vial contained billions of phage particles, purified to meet Australian Therapeutic Goods Administration standards. It remained potent for at least 18 months when stored at refrigerator temperatures.

In animal trials, Entelli-02 performed as well as the original mixture and even better against more virulent strains. Its diverse composition ensured that if one phage failed, others could still do the job. The team also found that Entelli-02 often worked well with antibiotics, creating a powerful combination against infections.

Bridging the Gap in Treatment

Although phage therapy has been around since the early 20th century, it fell out of favor with the rise of antibiotics. However, the growing problem of drug resistance has brought it back into focus.

What makes Entelli-02 unique is its approach. Instead of developing a broad-spectrum treatment or personalized medicine for each patient, the team created an “institutional cocktail” tailored to the most common bacteria found at The Alfred. This gives doctors a ready-to-use treatment that is both targeted and scalable.

“This is the first time we’ve designed and developed a clinical-ready phage therapy product tailored to an antimicrobial-resistant bacterial pathogen at a local hospital,” said Professor Jeremy J. Barr from Monash University. “Entelli-02 is not just a scientific achievement, it’s a clinical tool built for frontline use.”

Professor Anton Peleg, co-senior author and director of infectious diseases at The Alfred, added, “We’re bridging the gap between broad-spectrum antimicrobial treatments and personalized phage therapy to deliver a ready-to-use solution that’s both targeted and scalable.”

Practical Implications of the Research

Entelli-02 sets a new precedent for fighting hospital infections. Other hospitals could follow suit and develop their own phage cocktails tailored to local pathogens. This would provide doctors with a faster, more reliable option when antibiotics fail. The treatment also enhances existing medications, potentially extending the lifespan of remaining effective antibiotics.

Beyond ECC, this approach could be applied to other deadly bacteria that spread through surgical wards or intensive care units. While Entelli-02 is currently available only for compassionate use, clinical trials are ongoing. If successful, it could become a life-saving alternative for patients battling drug-resistant infections.

Research findings were published in the journal Nature Microbiology.