Isolation and in vitro characterization of novel S. epidermidis specific phages for therapeutic applications

S. epidermidis is the most frequent cause of chronic device-related infections being associated with biofilm growth. Increased tolerance to antibiotic therapy often requires prolonged treatment or revision surgery. Phage therapy is considered a viable option as adjunctive therapy to antibiotic treatment or as an alternative treatment for infections caused by S. epidermidis to prevent relapses. In the present study, we report on isolation and in vitro characterization of three new S. epidermidis phages. They infect a high proportion of clinically relevant S. epidermidis strains and several other coagulase-negative species growing in both planktonic culture and as biofilm. Based on biofilm phenotype and antibiotic resistance profiling, we selected clinical strains to further identify possible mechanisms behind increased tolerance to isolated phages. We also demonstrate the importance of informed decisions about selecting appropriate hosts for phage development from the beginning and address the in vitro efficacy testing.