When antibiotics fail: New guideline maps a path for personalized phage therapy

Clinical Takeaway: Personalized bacteriophage therapy may be considered for select patients with bacterial infections when guideline-based treatments have failed, are unavailable, or are not appropriate. The new consensus guideline emphasizes culture-confirmed pathogen identification, phage susceptibility testing, multidisciplinary oversight, and ongoing monitoring throughout treatment.

Bacteriophages, or viruses that selectively infect bacteria, have reemerged as a potential option for difficult-to-treat infections amid rising antimicrobial resistance. Although phage therapy has been used in compassionate-use settings worldwide, lack of standardized clinical and manufacturing guidance has limited broader adoption. The new consensus guideline, endorsed by multiple international infectious diseases organizations including IDSA, aims to provide a practical framework for integrating personalized phage therapy into clinical care.

Published in Nature Medicine, the guideline provides more than 60 recommendations spanning patient selection, infrastructure, phage preparation, quality control, administration, and future research priorities. The authors describe it as “the first detailed and consensus-based statement on personalized phage therapy” and say it “paves the way for the safe and standardized use of personalized phage therapy.”

Among the key recommendations, clinicians may consider personalized phage therapy for bacterial infections when standard-of-care treatments have failed or cannot be used. The document strongly recommends culture-based pathogen identification, antimicrobial susceptibility testing, and confirmation of bacterial susceptibility to selected phages as close to treatment initiation as possible. Phage therapy may also be considered in life-threatening situations before susceptibility results are available if broad-spectrum phage cocktails are accessible.

The guideline stresses multidisciplinary decision-making involving infectious disease specialists, microbiologists, pharmacists, and phage experts. For polymicrobial infections, all relevant pathogens should undergo phage susceptibility testing. Treatment plans should account for prior antibiotic exposure, infection severity and location, implanted devices, comorbidities, and concurrent medications.

Because phages are highly targeted and individualized, the guidance also establishes standards for phage sourcing, production, storage, labeling, and quality control. The authors recommend systematic documentation of cases in national or international registries to improve evidence generation and help address major knowledge gaps around efficacy, optimal dosing, and phage-antibiotic combinations.

Notably, the document concludes that available evidence suggests phage therapy is generally safe when appropriate quality standards are met, with no clear safety signals identified to date in children, immunocompromised patients, or during pregnancy, although data remain limited and decisions should be individualized.

Source: Würstle S, et al. (2026 Sep 21) Nat Med. A consensus-based guideline for personalized bacteriophage therapy