Characterization of <i>Enterococcus faecium</i> -Targeting <i>Minhovirus</i> Bacteriophages

Background: Enterococcus faecium are gram-positive, multidrug-resistant bacteria that are endemic in healthcare settings. Bacteriophage therapy could be an adjunctive treatment for E. faecium infections. Materials and Methods: We isolated four new Minhovirus phages using E. faecium strain ATCC 19434 as a host. Results: Phage genomes were each ∼19 kb in length, and were highly related to each other and to other previously isolated Minhovirus phages. Host range testing suggested a narrow spectrum of activity. In vitro -evolved phage-resistant mutants acquired mutations in the enterococcal polysaccharide antigen ( epa ) and capsular polysaccharide ( cps ) loci. Additional testing found that some phages were able to infect E. faecium clinical isolates with similar epa loci, further implicating epa as a putative receptor for Minhovirus phage infection. Conclusions: Overall, this study increases our understanding of phages that target E. faecium and increases the number of characterized phages that are active against this important pathogen.