The misuse and overuse of antibiotics have significantly increased the emergence of multidrug-resistant (MDR) bacteria, posing a high risk for global health. Bacteriophages (phages), natural co-evolving bacteria killers, are viruses that can infect and replicate inside specific bacterial cells, causing no innate harm to humans. The therapeutic use of phage to control bacterial infections was first proposed in the late 1910’s, but it was largely neglected in Western medicine due to the advent of antibiotics in the 1940's. Of late, the commercialization of new antimicrobials is slow. Therefore, phage therapy using obligately lytic phage for therapeutic purposes or as an adjunct to antibiotics is being revitalized in academic research in the West. This is a particularly advantageous strategy as new phage strains active against new bacterial strains can be found relatively quickly. The safety and efficacy of phage in treating patients against drug-resistant bacteria has been demonstrated through multiple clinical trials and cases of life-saving therapeutic use. 
Phage comprises a protein head containing the DNA materials and a tail with the total length ranged 50 ‒ 500 nm. Due to its large size and proteinaceous nature, direct delivery of phage to the respiratory tracts is the preferred route to achieve optimized therapeutic outcomes against lung infections. As preparing liquid phage formulations is relatively simple, nebulization has been the most popular approach to deliver phage for respiratory infections in early research. However, dry powder formulations are preferred over to liquid formulations in terms of storage, transportation and administration. Using two Pseudomonas phages (Podovridae PEV2 and Myoviridae PEV40) as model phages, we have previously demonstrated spray drying as a promising single-step process in producing inhalable phage dry powder formulations with sufficient long storage stability (≤ 1 log titer loss in 12 months) under refrigerated or room temperature at low humidity conditions (< 20% RH). As the phage powders were largely stabilized by an amorphous sugar in the solid state, handling and storing the powders at low humidity condition (RH <20%) is required to minimize the occurrence of recrystallization.  
Recently, we have extended the collected knowledge to formulate an inhalable Acinetobacter baumannii phage (vB_AbaM-IME-AB406). We also investigated the effect of high humidity condition upon the administration of phage powders on the stability of phage and in vitro aerosol performance with the aim to identify an optimal formulation suitable for global distribution, including area with subtropical climates where the average RH ≥ 65% all year round.

Dr. Sharon Shui Yee Leung completed her PhD (Chemical Engineering) in the University of Sydney in 2012. Then she received her postdoctoral training in the Faculty of Pharmacy in the University of Sydney with interest in developing technology platforms for the production of engineering particles for respiratory delivery. In 2014, she was awarded a Postdoctoral Fellowship from the Faculty of Pharmacy to develop technologies for aerosol delivery of bacteriophages to combat MDR bacteria. Sharon joined the School of Pharmacy at the Chinese University of Hong Kong in 2018. Her research focuses on the development of therapeutic phage and phage-encoded proteins to address the MDR threats.