Phage Therapy against Staphylococcus aureus : Selection and Optimization of Production Protocols of Novel Broad-Spectrum Silviavirus Phages.

Background: Phage therapy a promising antimicrobial strategy to address antimicrobial resistance for infections caused by the major human pathogen Staphylococcus aureus . Development of therapeutic phages for human use should follow pharmaceutical standards, including selection of strictly lytic bacteriophages with high therapeutic potential and optimization of their production process. Results: Here, we describe three novel Silviavirus phages active against 82% of a large collection of strains (n = 150) representative of various methicillin-susceptible and -resistant S. aureus clones circulating worldwide. We also investigated the optimization of the efficiency and safety of phage amplification protocols. To do so, we selected a well-characterized bacterial strain in order to (i) maximize phage production yields, reaching phage titres of 10 11 PFU/mL in only 4 h; and (ii) facilitate phage purity while minimizing the risk of the presence of contaminants originating from the bacterial host; i.e., secreted virulence factors or induced temperate phages. Conclusions: In sum, we propose a quality-by-design approach for the amplification of broad-spectrum anti- S. aureus phages, facilitating the subsequent steps of the manufacturing process; namely, purification and quality control.