Date of Award

January 2025

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Thomas S. Murray

Abstract

Background

The global rise of multidrug-resistant (MDR) Pseudomonas aeruginosa necessitates novel therapeutic approaches, particularly for patients with cystic fibrosis (CF). Bacteriophage therapy, delivered via inhalation, offers a targeted and potentially transformative treatment for pulmonary infections caused by MDR pathogens. This study aimed to evaluate the effects of nebulizer type and bacteriophage morphology on viable phage recovery and aerosol particle size distribution, hypothesizing that nebulizer-phage compatibility significantly influences the delivery of viable phages to the lower respiratory tract.

Methods

We conducted an in vitro study utilizing two clinically relevant nebulizer systems: the Pari LC Plus jet nebulizer and the Altera eFlow vibrating mesh nebulizer. Four phages with varying morphologies—OMKO-1, TIVP-H6, LPS-5, and MS2—were aerosolized through each device. The Next Generation Cascade Impactor was employed to measure aerosolized particle sizes and recover viable phages across defined aerodynamic size fractions. Data on viable phage recovery, particle size distribution, and respirable fractions (≤5.0 μm) were collected and analyzed using factorial ANOVA to assess the effects of phage morphology and nebulizer type.

Results

The results demonstrated significant variability in viable phage recovery and particle size distribution across nebulizer-phage combinations. The Pari LC Plus produced aerosols with a lower mass median aerodynamic diameter (MMAD) than the Altera eFlow (4.27 ± 1.03 μm vs. 5.85 ± 0.90 μm; p < 0.001), delivering a higher proportion of viable phages to the respirable fraction for all phage types except LPS-5. The OMKO-1 phage exhibited the greatest difference in viability between nebulizers, with the Pari LC Plus preserving 47.3% ± 5.0% of viable phages compared to 28.3% ± 22.1% for the Altera eFlow. In contrast, the control phage MS2 achieved the highest overall recovery, highlighting the structural advantages of tailless phages in maintaining viability during nebulization.

Conclusions

This study concluded that phage morphology and nebulizer type are critical determinants of aerosol delivery efficacy. Jet nebulizers, such as the Pari LC Plus, may be more effective for larger, tailed phages, while vibrating mesh nebulizers can deliver tailless phages with greater efficiency. These findings underscore the importance of tailoring phage-nebulizer pairings to optimize therapeutic outcomes. Future studies should focus on in vivo validation and the development of standardized protocols to advance the clinical application of inhaled phage therapy for MDR P. aeruginosa infections.

Comments

This is an Open Access Thesis.

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