Objective:

To report the clinical and microbiological outcomes of personalized phage therapy combined with colistin for a persistent multidrug-resistant Klebsiella pneumoniae prosthetic elbow infection following a war-related injury.

Approach:

• Patient Background: A 52-year-old man with multiple war-related injuries underwent total elbow arthroplasty and subsequently developed a prosthetic joint infection caused by multidrug-resistant K. pneumoniae harboring extended-spectrum β-lactamases and the OXA-48 and New Delhi metallo-β-lactamase carbapenemases.
• Initial Treatment: After 4 weeks of intravenous antibiotics, persistent drainage prompted a 14-week regimen of cefiderocol, fosfomycin, ertapenem, and colistin with repeated surgical debridement. Although temporary microbiological clearance was achieved, infection recurred.
• Phage Therapy Initiation: After failure of antimicrobial therapy and with informed consent, personalized phage therapy was initiated in combination with colistin as an adjunct to surgical debridement.
• Phage Preparation and Administration: A lytic phage active against all 6 patient isolates was selected, prepared under quality-control standards, and administered at 1.25 × 10^8 plaque-forming units both locally and intravenously alongside colistin. Local treatment was given once daily for 5 days, while twice-daily intravenous phage therapy was extended to a total of 56 days.

Key Findings:

• Relative bacterial load fell rapidly after treatment initiation, with a 3.52-log reduction during the first days and undetectable K. pneumoniae by day 8; consecutive cultures on days 12 and 15 and subsequent routine monitoring remained negative.
• Treatment was associated with progressive wound healing and partial recovery of elbow mobility, with no sign of infection recurrence during the 30 days of available follow-up after treatment completion.
• No adverse effects were reported, and C-reactive protein, glomerular filtration rate, and white blood cell counts remained stable, supporting good tolerability of the combined treatment.

Interpretation:

The case illustrates the potential role of personalized phage therapy as an adjunct to antibiotics and surgical debridement for complex prosthetic joint infections caused by multidrug-resistant K. pneumoniae when conventional treatment options are limited.

Limitations:

• Phage resistance could not be evaluated because no additional bacterial isolates were available after microbiological clearance.
• Whether phage monotherapy would have been equally effective remains unknown, and the in vivo effect of the observed neutralizing antibody response on phage efficacy was unclear.
• Long-term clinical success could not be definitively established because further follow-up was unavailable after the patient was repatriated.

Conclusion:

Combined phage-colistin therapy was associated with marked clinical improvement, microbiological clearance, progressive wound healing, partial recovery of elbow mobility, and avoidance of imminent limb amputation during the observed period. The case adds to clinical evidence supporting personalized phage therapy combined with conventional surgical and antimicrobial treatment for multidrug-resistant infections while underscoring the need for well-designed clinical trials to establish efficacy and routine implementation.