Isolation and characterization of a novel phage belonging to a new genus against Enterococcus faecium.

Enterococcus faecium is a Gram-positive bacterium commonly found in the intestines of humans and animals. While certain strains exhibit probiotic properties, others have become significant pathogens due to their high level of antibiotic resistance. Bacteriophages, as natural bacterial predators, have emerged as promising alternatives for controlling bacterial infections, especially antibiotic-resistant strains. In this study, we isolated and characterized a novel bacteriophage, Enterococcus phage XWef1, which targets E. faecium, from waste materials of a feed additive production industry. The phage displayed optimal activity at pH levels between 6 and 8, with high stability at temperatures below 40 °C. It exhibited a narrow host range. Genomic analysis revealed 63 open reading frames (ORFs), including genes related to structural proteins, DNA replication, and host lysis. The comparative genomic analysis showed that XWef1 has less than 70% intergenomic similarities with its most similar phages. Thus, we propose that XWef1 is a novel Enterococcus phage belonging to a new genus. The discovery of XWef1 not only enriches our understanding of phage diversity but also offers new perspectives for phage research and development, with promising implications for microbial control and therapeutic applications.