Isolation and Characterization of the Lytic Enterococcus faecium Phage φEc-ZZ2

Abstract

Infections with vancomycin-resistant Enterococcus (VRE) have been increasingly reported, especially in immunocompromised patients. Bacteriophages (phages) are often considered as potential therapeutic candidates in treating infectious diseases. To search for therapeutic phages as antimicrobial agents for the treatment of Enterococcus faecium infections, eight E. faecium phages were isolated from the environments. One of these, phage φEc-ZZ2, which was capable of eliciting efficient lysis of E. faecium, was selected for analysis. Transmission electron microscopy revealed its resemblance to members of the family Siphoviridae, with a tail 200 nm long and an icosahedral head 45 nm in diameter. Phage φEc-ZZ2 exhibited rapid adsorption (> 99% adsorbed in 10 min), a short latency period of 20 min and a large burst size of 180 PFU/cell. Host range determination shows that φEc-ZZ2 has a relatively broader host range (specificity for 54.5% of tested E. faecium strains). Furthermore, when φEc-ZZ2 alone was incubated at different pH, the phage was stable over a wide pH range (5 to 9). These characteristics of φEc-ZZ2 will provide useful information for further research on the interaction between Enterococcus phages and their hosts. Moreover, in consideration of its pH stability and broader host range, φEc-ZZ2 may be a good candidate as a therapeutic/disinfectant agent to control nosocomial infections caused by E. faecium.