Klebsiella pneumoniae is a common nosocomial pathogen, with high incidence of extended-spectrum-β-lactamase-resistance leading to poor patient outcomes. With the continued emergence of antibiotic resistant K. pneumoniae, including highly resistant strains producing the blaKPC carbapenemase, alternative treatment options are under investigation. Bacteriophages, as major natural predators of bacteria, are a promising alternative antimicrobial, but their use requires thorough characterization of candiate phages. This work aims to determine the receptors used by 30 lytic bacteriophages, and determine if phages are able to evolve in vitro to overcome loss of their receptor. A collection of 30 virulent phages were isolated against a panel of clinically relevant K. pneumoniae isolates carrying a blaKPC allele. Phage-resistant bacterial mutants were isolated against each phage, and the mutant genomes sequenced to identify mutations associated with phage resistance. Mutations in the bacterial capsule, LPS synthesis loci, or outer membrane proteins were associated with phage resistance. Complementation of the mutant genotypes and phage adsorption phenotypes is ongoing.A system to select for phage mutants that are able to overcome bacterial resistance was developed, exploiting the natural ability of phages to evolve along with their predators to see if these phages can expand their host range. In experiments to date, only a subset of phages appear able to overcome host resistance by evolution in vitro. This work will assist in identifying phages that would make the most effective therapeutic cocktails while overall reducing the possibility of an ineffective treatment due to the emergence of phage resistance.