From resistance to response: Bacteriophages in multidrug-resistant Mycobacterium abscessus after lung transplantation.

We report a case series of 2 lung transplant recipients with chronic, multidrug-resistant Mycobacterium abscessus infections unresponsive to conventional antibiotic therapy, who received intravenous bacteriophage treatment for 12 months under compassionate use. Both patients showed clinical improvement and resolution of the radiological opacities. Gene expression in blood samples collected before and 24 hours after initiation of phage therapy was analyzed using the NanoString Host Response panel, revealing immune activation, with increased expression of proinflammatory genes (CXCL10 and IL8) and decreased expression of immune evasion pathways (ULK1 and AKT1). These exploratory findings provide insight into potential mechanisms by which bacteriophages may modulate host immunity and support bacterial clearance. Overall, the results suggest that long-term bacteriophage therapy may offer a safe and effective adjunct for managing refractory M. abscessus infections in immunocompromised individuals with chest-localized infection.