Abstract
Enterococcus faecalis is increasingly becoming an important nosocomial infection opportunistic pathogen. E. faecalis can easily obtain drug resistance, making it difficult to be controlled in clinical settings. Using bacteriophage as an alternative treatment to drug-resistant bacteria has been revitalized recently, especially for fighting drug-resistant bacteria. In this research, an E. faecalis bacteriophage named IME-EF1 was isolated from hospital sewage. Whole genomic sequence analysis demonstrated that the isolated IME-EF1 belong to the Siphoviridae family, and has a linear double-stranded DNA genome consisting of 57,081 nucleotides. The IME-EF1 genome has a 40.04% G+C content and contains 98 putative coding sequences. In addition, IME-EF1 has an isometric head with a width of 35 nm to 60 nm and length of 75 nm to 90 nm, as well as morphology resembling a tadpole. IME-EF1 can adsorb to its host cells within 9 min, with an absorbance rate more than 99% and a latent period time of 25 min. The endolysin of IME-EF1 contains a CHAP domain in its N-terminal and has a wider bactericidal spectrum than its parental bacteriophage, including 2 strains of vancomycin-resistant E. faecalis. When administrated intraperitoneally, one dose of IME-EF1 or its endolysin can reduce bacterial count in the blood and protected the mice from a lethal challenge of E. faecalis, with a survival rate of 60% or 80%, respectively. Although bacteriophage could rescue mice from bacterial challenge, to the best of our knowledge, this study further supports the potential function of bacteriophage in dealing with E. faecalis infection in vivo. The results also indicated that the newly isolated bacteriophage IME-EF1 enriched the arsenal library of lytic E. faecalis bacteriophages and presented another choice for phage therapy in the future.
Highlights
Enterococcus faecalis and Enterococcus facium belong to Gram-positive bacteria that commonly inhabit the lower intestinal tract, oral cavity, and vaginal tract of humans or animals
E. faecalis is used as a starter for fermented food and probiotics [4], the bacterium can cause endocarditis and bacteremia, urinary tract infections, meningitis, and other infections in humans
The results showed that the phage IME-EF1 had a latent period time of 25 min and a burst size of 60 plaque forming unit (PFU)/infected bacteria when infecting its host bacteria E. faecalis 002
Summary
Enterococcus faecalis and Enterococcus facium belong to Gram-positive bacteria that commonly inhabit the lower intestinal tract, oral cavity, and vaginal tract of humans or animals. E. faecalis is used as a starter for fermented food and probiotics [4], the bacterium can cause endocarditis and bacteremia, urinary tract infections, meningitis, and other infections in humans. A plasmid-encoded hemolysin, called the cytolysin, is important for pathogenesis in animal models of infection, whereas cytolysin combined with high-level gentamicin resistance is associated with a five-fold increase in risk of death in human bacteremia patients [9,10,11]. Enterococci resist bile salt detergents, heavy metals, ethanol, azide, and desiccation, and can grow at 10 °C to 45 °C and survive at 60 °C for 30 min [7]. Nosocomial infection caused by E. faecalis or E. facium is becoming a major concern in hospital settings because acquisition of virulence or antibiotic resistance makes this bacterium more difficult to be controlled
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