The Influence of Formulation Components and Environmental Humidity on Spray-Dried Phage Powders for Treatment of Respiratory Infections Caused by Acinetobacter baumannii

Abstract

The feasibility of using respirable bacteriophage (phage) powder to treat lung infections has been demonstrated in animal models and clinical studies. This work investigated the influence of formulation compositions and excipient concentrations on the aerosol performance and storage stability of phage powder. An anti-Acinetobacter baumannii phage vB_AbaM-IME-AB406 was incorporated into dry powders consisting of trehalose, mannitol and L-leucine for the first time. The phage stability upon the spray-drying process, room temperature storage and powder dispersion under different humidity conditions were assessed. In general, powders prepared with higher mannitol content (40% of the total solids) showed a lower degree of particle merging and no sense of stickiness during sample handling. These formulations also provided better storage stability of phage with no further titer loss after 1 month and <1 log titer loss in 6 months at high excipient concentration. Mannitol improved the dispersibility of phage powders, but the in vitro lung dose dropped sharply after exposure to high-humidity condition (65% RH) for formulations with 20% mannitol. While previously collected knowledge on phage powder preparation could be largely extended to formulate A. baumannii phage into inhalable dry powders, the environmental humidity may have great impacts on the stability and dispersion of phage; therefore, specific attention is required when optimizing phage powder formulations for global distribution.

Design of respirable sprayed microparticles of encapsulated bacteriophages

“…The combination of lactose, trehalose, and leucine can further enhance the protection of the bioactive compound. Formulations containing 40% trehalose, 40% mannitol, and 20% leucine had better storage stability, under storage conditions of −4 °C and 30% relative humidity, of P. aeruginosa phage with no further phage loss after 1 month and <1 log storage loss (Yan et al, 2021). The presence of leucine also supports the storage and of phages.…”

“…The presence of leucine also supports the storage and of phages. Spray-dried powder containing 80% lactose, 20% leucine, and podovirus phage can be stored and handled below 60% RH to prevent crystallization; they stay stable for 1 year at 15% humidity and humidity 20 ° (Yan et al, 2021).…”

Navigating ESKAPE Pathogens: Considerations and Caveats for Animal Infection Models Development

“…Pneumonia is modeled by intranasal instillation of bacterial suspensions between 10 7 and 10 8 CFU/mL, sepsis through intraperitoneal (IP) injections ranging from 10 8 to 10 9 CFU/mL, and urinary tract infections through transurethral catheterization with bacterial inocula from 10 8 to 10 10 CFU/mL. 48 These models represent the primary clinical manifestations of the pathogens, enabling detailed investigations into their virulence and therapeutic responses. For P. aeruginosa , chronic respiratory infections, acute pneumonia, and biofilm-associated infections are studied.…”

Pulmonary Delivery of Emerging Antibacterials for Bacterial Lung Infections Treatment

“…Since most sugar excipients, particularly trehalose and lactose, remained in the amorphous form to stabilize the incorporated phage, they are prone to recrystallization upon exposure to moisture in the environment. Handling and storing the phage powders at low humidity conditions are essential to ensure the phage stability within powders and their dispersibility [ 108 ]. Comparatively, the impacts of storage temperature on the phage powders seems to be less critical for phage powder.…”