Phage therapy for Staphylococcus aureus: assessment of the therapeutic potential and optimization of efficiency and safety of production protocols of broad-spectrum Silviavirus phages

Phage therapy is one of the promising antimicrobial strategy to face antimicrobial resistance for infections due to the major human pathogen Staphylococcus aureus. Development of phage products should follow pharmaceutical standards including selection of strictly lytic bacteriophages with high therapeutic potential and optimization of their production process. Here, we report the description of 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 performed optimization of efficiency and safety of phage amplification protocols. To do so, we selected a well-characterized bacterial strain i) to maximize phage production yields, reaching phage titres of 1011 PFU/mL in 3 to 4h and ii) to facilitate phage purity while minimizing the risk of contamination by contaminants originating from the bacterial host, i.e. secreted virulence factors or induced temperate phages. All together, 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.