Background and objectives We have recently established safety and efficacy of nasally-inhaled bacteriophage (phage) against Pseudomonas aeruginosa in a murine model with reduced infective burden and inflammatory response demonstrated in bronchoalveolar lavage (Thorax 2012;67:A50–A51 doi:10.1136/thoraxjnl-2012–202678.108). The aim of this study was to assess titre and activity of four phages following exposure to nebuliser systems more applicable to clinical trial use.
Methods Four phage strains (1–4) were nebulised through a) Pari LC Plus (LCP), b) Aeroeclipse II (AE) and c) eFlow Rapid for up to 15 min. Phages were collected downstream and quantified by standard plaque assay against Pa01. Results were compared with controls exposed to the nebulisation chambers for 15 min.
Results All phages retained efficacy post-nebulisation. Nebuliser type affected recovered titres:
LCP caused significant decrease in titres of phage 1 and 2 within 5 min and phage 3 within 15 min (p < 0.05). Phage 4 titre did not drop.
AE, despite similar mode of action to LCP, was not as detrimental to titres. Decrease in phage 1 titre was seen within 15 min, phage 2 within 10 min (p < 0.05). Phage 3 and 4 did not decrease (p > 0.05).
eFlow does not continuously nebulise and recirculate phage, hence changes in titre over time were not recorded. No titre decreases were observed at end of nebulisation (p > 0.05).
Morphology may play a role in maintenance of phage titre post-nebulisation (1 and 2 Myoviridae, 3 and 4 Podoviridae).
The Figure 1 shows changes in titres of phage 3 over time following nebulisation through each system.
Conclusions Phage efficacy was retained after nebulisation though titres dropped, greatest for LCP and least for eFlow (which fell within variability of the methodology (± 0.5 log)). We confirm that phage can survive nebulisation and that this mode of administration may therefore be appropriate for future clinical trials.