Characterization of Enterococcus faecium-Targeting Minhovirus 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.