Personalized Phage Therapy in an ICU Patient with Polymicrobial Pulmonary Infections: a case from a single-arm trial

Ventilator-associated infections (VAIs) caused by multidrug-resistant (MDR) pathogens poses a significant challenge in intensive care units (ICUs). Phage therapy has emerged as a promising alternative for VAIs, though its efficacy depends on multiple factors. We report a 40-year-old male ICU patient with sequential pulmonary infections of MDR Acinetobacter baumannii, Klebsiella pneumoniae, and Stenotrophomonas maltophilia. Seven rounds of tailored phage therapy-targeting single or dual pathogens-were administered adjunctive to antibiotics. A. baumannii was complete eradication, but K. pneumoniae and S. maltophilia showed cyclical clearance and recurrence due to strain replacement and phage resistance. Phage therapy correlated with reduced bacterial load, fever, procalcitonin, and IL-6 levels, alongside improved pulmonary inflammation, while white blood cell counts and C-reactive protein showed limited response. No severe adverse events occurred. Dynamic shifts in dominant pathogens aligned with clinical progression, with phage therapy providing transient control, extending the window for intervention and reducing high-level antibiotic use. After six months, the patient was weaned from ventilation and discharged. This case underscores the complexity of VAI management and highlights the potential of personalized phage therapy to mitigate MDR infections and minimize antibiotic reliance. This case was enrolled in a single arm trial (ChiCTR2000036801).