**6.3 Formulations of phage-antibiotic combination to treat lung infections**

*Streptococcus pneumoniae, S. aureus, B. cepacia complex, Klebsiella pneumonia* and *P. aeruginosa* are the major causative pathogens for lung infections. A summary on previous work on the combination phage-antibiotic therapy against these pathogens were provided in Chang et al. [8]. Recently, Lin et al. screened a panel of antibiotics with PEV20 phage to target two *P. aeruginosa* strains and ciprofloxacin showed the highest synergistic effects. The combination was then nebulized using a jet nebulizer and a mesh nebulizer with no difference in the antibacterial effect observed between the nebulized samples and non-nebulized suspension [89]. Later, the same research team investigated the feasibility of formulating this combination into dry powder formulations [90]. PEV20 phage and ciprofloxacin were co-spray dried with leucine and with or without lactose. Both formulations maintained bactericidal synergy after dispersion using a low resistance inhaler or a high resistance inhaler, both showing acceptable FPF (60–75%). The antimicrobial efficacy of the PEV20-ciprofloxacin combination powder was also confirmed in a mice respiratory infection model with significant bacteria reduction (5.9 log) at 24 h post-treatment, while no loss of bacteria viability when mice was treated with phage or antibiotics alone [91]. The long-term storage stability of the combination powder at 4 °C and 20% R.H. was also confirmed [92].
