Jet nebulization of bacteriophages with different tail morphologies – structural effects

Abstract

It was previously demonstrated that the loss of infectivity of a myovirus PEV44 after jet nebulization was closely related to a change in bacteriophage (phage) structure. In this follow-up study, we further examined the impact of jet nebulization on tailed phages, which constitute 96% of all known phages, from three different families, Podoviridae (PEV2), Myoviridae (PEV40) and Siphoviridae (D29). Transmission electron microscopy (TEM) identified major changes in phage structures after jet nebulization, correlating with their loss of infectivity. For the podovirus PEV2, jet nebulization had a negligible impact on activity (0.04 log10¬ pfu/mL loss) and structural change. On the other hand, the proportion of intact phages in the nebulised samples dropped from 50% to ~27% for PEV40 and from 15% to ~2% for D29. Phage deactivation of PEV40 measured by the TEM structural damage (0.52 log10¬ pfu/mL) was lower than that obtained by plaque assay (1.02 log10 pfu/mL), but within the range of variation (± 0.5 log10 pfu/mL). However, TEM quantification considerably underestimated the titer reduction of D29 phage, ~ 2 log pfu/mL lower than that obtained in plaque assay (3.25 log10 pfu/mL). In conclusion, nebulisation-induced titre loss was correlated with morphological damage to phages and in particular, the tail length may be an important consideration for selection of phages in inhaled therapy using jet nebulization.