Phage therapy gets its first major playbook

As antibiotic resistance continues to outpace the development of new drugs, bacteriophages — viruses that selectively infect and kill bacteria — are gaining renewed attention. An international working group led by the German Society for Infectious Diseases, involving 20 professional societies and 18 global experts, has published a landmark consensus guideline in Nature Medicine outlining how phage therapy should be selected, prepared, administered, and monitored.

The guidelines position phage therapy as a personalized, case-by-case option — not a standard treatment — for patients when conventional antibiotics have failed or are unavailable. Each case should be reviewed by an interdisciplinary team including the treating physician, a clinical microbiologist, and a recognized phage expert. A "phage match" test must also be performed before treatment to confirm the phage works against the specific bacterial strain involved.

By the Numbers

• 60+ recommendations covering phage selection, quality control, administration, and monitoring
• 77% of patients in a Belgian case series of 100 showed clinical improvement
• 61% had target bacteria become undetectable after treatment
• ~10,000 patients in Germany alone may be eligible for phage therapy based on multidrug-resistant infection rates

Why it matters: With few new antibiotics entering the market, phage therapy could become a critical tool against multidrug-resistant infections. These guidelines give clinicians a structured framework to use it responsibly — while the push for stronger clinical trial evidence continues.