(494) Bacteriophage Distribution on Aerosolized Particles

Background: Inhaled bacteriophage are being studied in clinical trials as a novel approach to treat multi-drug resistant (MDR) bacterial infections. However, the ideal dose and the optimum nebulizer set up to deliver different bacteriophage used in clinical studies has not been determined. This study sought to characterize how various nebulizers affect the distribution and recovery of phage on aerosolized particles in the airway, providing insight into how far aerosolized phage can deposit in the lower respiratory tract. Additionally, this study considered whether different phage species are distributed in equivalent patterns.

Methods: A refrigerated Next Generation Impactor (NGI) was used to measure bacteriophage dispersion on different aerosolized particle sizes generated by either a Pari LC Plus, Phillips Sidestream, or Phillips Sidestream Plus nebulizer. The Escherichia coli, MS2 phage was tested along with two clinical phages (pB and INF) used at our center for MDR Pseudomonas aeruginosa. Albuterol concentrations were used to determine the mass median aerodynamic diameter (MMAD) for each nebulizer as an estimate of function. Next, three-five ml of sterile dH₂O inoculated with different bacteriophage was nebulized through the NGI for 7 minutes. Liquid in the NGI collecting cups containing aerosolized particles of various sizes were then harvested and phage plaques were quantified.

Results: The MMAD’s for all three nebulizers tested was < 5μM, suggesting they are all able to effectively deliver aerosols to the lower respiratory tract. Recovered viable phage after nebulization ranged from 6.1 X10⁴- 2.7x10⁵. The pattern of phage recovery on different aerosolized particle sizes was similar for all three nebulizers with most phage recovered on particle sizes from 2.08-5.39μM with >50% of recovered phage in the respirable fraction. More viable MS2 phage was recovered from the Phillips Sidestream Plus than from other nebulizers. Using the Sidestream Plus, the recovery of the clinical phages pB and INF were proportionally higher than MS2, suggesting the individual phage properties may influence the distribution or survivability of viable phage (Table 1).

Conclusions: Viable phage are effectively aerosolized by a variety of different nebulizers onto particles capable of reaching the lower airway with the Phillips Sidestream Plus being most effective. The proportion of clinical phage recovered was high suggesting this is an efficient way to distribute phage in patients with chronic MDR infection.

Acknowledgements: This work was supported by internal funding from the Yale School of Medicine

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