Manufacturing and ambient stability of shelf freeze dried bacteriophage powder formulations

The severity of multidrug resistance to antibiotics has urged development of alternative treatment approaches, including bacteriophage therapy. Given the complexity of the bacteriophage structure, formulation and stability are primary concerns. Our present work optimized process and formulations of phage powder manufacturing and investigated the stability of lyophilized bacteriophage powders under ambient storage. The model phage M13 was formulated with trehalose, mannitol, sucrose and PEG₆₀₀₀ and lyophilized in different conditions. Bacteriophage viability was examined by titering and was considered as the assessment of phage stability. Less titer loss of trehalose and sucrose formulations were observed compared to mannitol and PEG groups both immediately after lyophilization and upon long term storage. When evaluating lyophilization conditions, an additional 1 log titer was preserved by reduction of product drying stress. Trehalose was stabilized in the amorphous state whereas mannitol stayed in crystalline state in lyophilized powders. Increased moisture content was demonstrated to have a positive impact on viability of phage after lyophilization and upon storage. Overall, 2% trehalose or sucrose (w/v) can sufficiently stabilize phage during lyophilization process and storage in ambient conditions. There is a positive correlation between residual water and stability of phage. These collective findings highlight the potential of long-term, ambient storage of bacteriophage towards their successful use in diverse healthcare settings.