vB_EfaH_163 phage reduces the mortality of an E. faecium vanR clinical isolate in a Galleria mellonella animal model

Resumen del trabajo presentado en el I Asturias International Meeting on Clinical Microbiology and Infectious Diseases - AIMID , celebrado en Oviedo (España) , los días 22 y 23 de septiembre de 2022
Introduction The rise of antimicrobial resistant (AMR) bacteria is a major health concern, especially with regard to members of the ESKAPE group, to which vancomycin-resistant Enterococcus faecium (VRE) belongs. Phage therapy has emerged as a novel alternative for the treatment of AMR infections. However, it relies on the isolation and characterization of a large collection of phages. This work describes the exploration of human faeces as a source of new E. faecium-infecting phages. Material and methods Phage vB_EfaH_163 was isolated from the faeces of a human volunteer after applying a microbiota separation method. Phage vB_EfaH_163 was then characterized at the microbiological level: Host range against strains of E. faecium from different origins -including VRE clinical isolates- capsid morphology, and one-step growth curve. The vB_EfaH_163 genome was sequenced and analysed. In addition, technological characterization-specifically pH and thermal stability- was performed. Finally, the biocontrol capacity of vB_EfaH_163 against a clinical VRE strain was assayed in broth and in a Galleria mellonella animal model. Results and discussion vB_EfaH_163 phage is a new member of Herelleviridae, subfamily Brockvirinae. Its genome consists in a dsDNA genome of 150.836 bp that do not harbours any toxin-encoding or antibiotic resistance genes. It infects a wide range on E. faecium strains of different origin, including VRE strains. Interestingly, it can also infect E. faecalis strains, even some that are linezolid-resistant. Its capacity to control the growth of a clinical VRE isolate was shown in broth culture. Moreover, the phage vB_EfaH_163 was shown to significantly reduce mortality in a Galleria. mellonella animal model of E. faecium infection. The discovery and characterization of vB_EfaH_163 increases the number of phages that might be used therapeutically against AMR bacteria.