Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2023

Assessing the effects of aerosolisation on bacteriophage viability and activity against P. aeruginosa (#127)

Rohan Flint 1 2 , Daniel R Laucirica 2 , Barbara Chang 3 , Stephen M Stick 2 4 5 , Anthony Kicic 2 4 5 6 , ARESTCF 2 5 7 8 , WAERP 2 9
  1. School of Biomedical Sciences, University of Western Australia, Perth, Western Australia, Australia
  2. Wal-yan Respiratory Research Centre, Telethon Kids Institute, University of Western Australia, Perth, Western Australia, Australia
  3. The Marshall Centre for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Perth, Western Australia, Australia
  4. Centre for Cell Therapy and Regenerative Medicine, School of Medicine and Pharmacology, University of Western Australia and Harry Perkins Institute of Medical Research, Perth, Western Australia, Australia
  5. Department of Respiratory and Sleep Medicine, Perth Children's Hospital, Perth, Western Australia, Australia
  6. School of Population Health, Curtin University, Perth, Western Australia, Australia
  7. Murdoch Children's Research Institute, Melbourne, Victoria, Australia
  8. Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
  9. St. John of God Hospital, Perth, Western Australia, Australia

Introduction & Aims: Lower respiratory tract infections (LRTIs) are a leading cause of mortality worldwide [1]. Individuals with chronic respiratory diseases including cystic fibrosis (CF) are especially susceptible to LRTIs by bacterial pathogens such as Pseudomonas aeruginosa, which can become antimicrobial resistant (AMR) [2]. Bacteriophages (phages) are a promising alternative therapy against AMR infections; however, how phages retain their activity after delivery to the lungs via an aerosol is not well studied. For use as a therapeutic, <1 log10 reduction is considered a minimal loss of phage titre following aerosolisation [3, 4]. Here, we sought to test the effect of aerosolised delivery on the infectivity of P. aeruginosa phages.

Methods: Six phages (79.U1, 79.U2, 4.U3, E79, Boorn-mokiny-1, Kara-mokiny-16) from the Myoviridae family were individually nebulised using a vibrating-mesh nebuliser (Aerogen Pro). Nebulisation was performed into collection tubes to harvest aerosol condensate, infectious titre pre and post nebulisation was assessed via plaque assay of original and nebulised samples and expressed as plaque forming units per mL of sample (PFU/mL). Titre reduction values were compared to the acceptable level in the literature (<1 log10 reduction).

Results: Nebulisation resulted in a reduction of infectious titre for all six phages tested (values are presented as average log10 reduction ± SD PFU/mL) - KM-16: 0.49 ± 0.08, E79: 0.41 ± 0.13, BM-1: 0.11 ± 0.09, 4.U3: 0.27 ± 0.06, 79.U2: 0.20 ± 0.11, 79.U1: 0.08 ± 0.06. Loss of active phages ranged between 0.08 and 0.49 log10, below the acceptable threshold of loss for therapeutic use. In addition, reduction in infectivity for all nebulised phages was not significant (p > 0.05).

Conclusion: Phages can be aerosolised by vibrating-mesh nebulisation with minimal reduction in infectivity. Data generated suggests that aerosolisation is a feasible delivery method for phages against respiratory pathogens. Future work will test phages from various families to identify phage groups with high retention of activity in an aerosol, as well as buffers and adjuvants that may further stabilise phages during aerosolisation. Phage preparations will also be aerosolised with different delivery devices to ensure phage stability across a range of devices used by patients.

  1. WHO, The top 10 causes of death. World Health Organization, 2018.
  2. Pillarisetti, N., et al., Infection, inflammation, and lung function decline in infants with cystic fibrosis. Am J Respir Crit Care Med, 2011. 184(1): p. 75-81.
  3. Carrigy, N.B., et al., Anti-tuberculosis bacteriophage D29 delivery with a vibrating mesh nebulizer, jet nebulizer, and soft mist inhaler. Pharmaceutical research, 2017. 34(10): p. 2084-2096.
  4. Hoe, S., et al., Respirable bacteriophages for the treatment of bacterial lung infections. Journal of aerosol medicine and pulmonary drug delivery, 2013. 26(6): p. 317-335.