RecruitingBiological interventionBiomarkers of Phage Treatment Response in NTM and Other InfectionsThis study aims to identify biomarkers associated with response to phage therapy for refractory bacterial infections. This includes mycobacteriophage treatment for patients with nontuberculous mycobacterial infections. Blood and airway samples will be obtained from follow up visits of patients with refractory bacterial infections that are considered for phage therapy. Samples will be compared between those that receive phage therapy and those that did not. Biomarkers will include changes in the airway microbiome, transcriptome, inflammatory cytokines, and development of neutralizing antibody against phages. The primary endpoint is to identify biomarkers associated with clinical and/or radiographic improvement and/or culture improvement which includes clearing of cultures or decrease in qualitative or resolution of signs and symptoms of infection after at least 6-8 weeks of bacteriophage therapy.