One Hundred Cases That Mapped the Real-World Power of Phages

By the 2020s, dramatic single-patient rescues like the Patterson and Holdaway cases had made headlines, but a stubborn question lingered: were these miracles or anecdotes? With no large randomized trials yet completed, the field needed something between a case report and a controlled trial — a careful, systematic accounting of what actually happens when phage therapy is deployed in the real world, across many patients, pathogens, and hospitals. A consortium led from Belgium set out to provide exactly that.

Anchored by Jean-Paul Pirnay and colleagues at Queen Astrid Military Hospital in Brussels — a long-standing European hub for phage work — the group compiled the first 100 consecutive cases of personalized bacteriophage therapy that their network had facilitated between January 2008 and April 2022. The scope was striking: the infections were treated across 35 hospitals in 29 cities and 12 countries, making this a multicentre, multinational, retrospective observational study. These were not easy patients. They were people with difficult-to-treat, often life-threatening infections for whom conventional antibiotics had failed or were failing — chronic bone and joint infections, lower respiratory tract infections, skin and soft-tissue infections, and more.

The approach was rigorously personalized. Rather than reaching for an off-the-shelf product, the consortium matched phages to each patient's specific bacterial isolate, drawing on combinations of 26 individual bacteriophages and 6 defined cocktails. In some cases phages were even pre-adapted — trained in the lab against the patient's own strain to sharpen their killing power. This bespoke philosophy, treating phage therapy as precision medicine rather than a one-size-fits-all drug, defined the consortium's method.

The results, published in Nature Microbiology in 2024, were cautiously encouraging. Clinical improvement was reported in 77.2% of infections, and eradication of the targeted bacteria was achieved in 61.3%. For patients who had exhausted standard options, those numbers represented meaningful hope. But the study's most important and durable lesson lay in a single statistical finding about how phages and antibiotics interact.

The analysis found that bacterial eradication was about 70% less probable when no concomitant antibiotics were given alongside the phages — an odds ratio of roughly 0.3 for the no-antibiotic scenario. In plain terms, phage therapy worked far better as a partner to antibiotics than as a replacement for them. This reframed a common misconception. Phages are often pitched as a post-antibiotic alternative, a weapon for the day antibiotics stop working entirely. The Belgian cohort suggested the more powerful near-term role is synergy: phages and antibiotics together can accomplish what neither reliably achieves alone. Phages can knock down resistant populations, strip protective biofilms, and — through evolutionary trade-offs — even resensitize bacteria to drugs they had defeated. The consortium framed the message as 'making antibiotics great again.'

The authors were forthright about the study's limitations. A retrospective observational series cannot prove causation the way a randomized controlled trial can; there is inherent selection in which patients get treated and reported, treatments varied widely, and outcomes were assessed without the rigorous blinding a trial demands. The 100 cases are a foundation, not a verdict.

Yet the contribution was substantial. The study offered the largest systematically analyzed real-world dataset of personalized phage therapy to that point, gave clinicians realistic expectations for success rates, and — most consequentially — delivered hard evidence that phage-antibiotic combination should be the default design for the controlled trials the field still urgently needs. It moved phage therapy a step closer to the evidentiary mainstream, trading the drama of single rescues for the quieter authority of numbers.