Phage Therapy Using Phage Cocktails Against Enterococcus faecalis.

Objectives: Enterococcus faecalis is the major pathogen found in persistent infections associated with root canal treatment failure. Post treatment disease has been attributed to the lack of anti-infective strategies to eradicate intra-canal E. faecalis biofilms.
Phage therapy has proven to be effective against various photogenic bacteria. The objective here was to develop new treatments against E. faecalis biofilms using specific bacteriophages and to evaluate their efficacy in a human root canal infection model.
Methods: Here two E. faecalis-infecting bacteriophages were isolated from sewage water. These phages termed as EFDG1 and EFLK1 were visualized by electron microscopy and their coding sequences and phylogeny were determined by whole genome sequencing. Antibacterial activity was evaluated in vitro against planktonic and biofilm cultures using classical microbiology methods.
Results: The antibacterial activity of each one of them showed pros and cons, i.e. EFDG1 efficiently eradicated E. faecalis in logarithmic phase while EFLK1 was highly effective against stationary phase. Combination of the two anti-E. faecalis phages in cocktails showed efficacy against cultures in all growth stages. Combinations of 1:1 and 2:1 of EFDG1 and EFLK1 respectively, were found to be the best, compensating the shortcomings of each phage individually. Moreover, the cocktails were efficient against E. faecalis also in an ex-vivo post treatment human root canal model.
Genome sequencing showed that both phages belong to the Spounavirinae subfamily of the Myoviridae phages, which includes some of the most promising candidates for therapy of Gram positive pathogens with no apparent harmful genes.
Conclusions: In Conclusions, we show here that phage therapy using a cocktail of EFDG1 and EFLK1 is a promising approach to eradicate multidrug resistant VRE E. faecalis infections.