Phages Sustained Release to Target E. faecalis

Objectives: Vancomycin resistant Enteroccocus faecalis (E. faecalis) was described lately as one of the greatest threats to human health by the WHO. Bacteriophages (phages) offer an alternative way to target multidrug resistant bacteria. Local delivery of phages was shown as a successful method of delivery, but there is no former information about sustained release of E. faecalis phages. The null hypothesis here was that EFDG1 and EFLK1 phages, previously isolated by us, may be effective against VRE as a sustained release drug.
Methods: Phages were formulated into a slow release system. The formulation was placed in transwell inserts that were placed in a 24 wells plate and incubated with PBS at 37°C. The PFU/mL of the phages released to the PBS was measured using the standard double-layered agar method after different time slots, until 1 month. The activity against E. faecalis was evaluated in logarithmic and stationary growth using an Elisa plate reader, and the number of surviving bacteria was evaluated by CFU/mL.
Results: Phages survived in the formulation and kept an efficient activity against E. faecalis for at least 1 month. The formulation was highly efficient against both logarithmic and stationary E. faecalis, especially when a two phages cocktail was used. Live bacterial counts showed a decrease of up to 4 logs.
Conclusions: Phages can target vancomycin resistant E. faecalis efficiently in a sustained release medium.