Electrospray versus Nebulization for Aerosolization and Filter Testing with Bacteriophage Particles

Abstract

Aerosolization of bacteriophage MS2 virions by nebulization and charge-reduced electrospray were compared during testing of three filter media. Sample swatches were taken from a surgical mask, N95 filtering-facepiece respirator (FFR), and N100 FFR for use in repeated, short-duration (15 min) penetration tests with bacteriophage MS2 aerosolized by nebulizer and electrospray. Evaluated were (1) the virus suspension preparation protocol, (2) resulting particle size distribution, count stability, and count variability, and (3) the ability to generate culturable MS2 virions. While preparation of the electrospray bacteriophage suspension required additional purification and concentration steps and took more time than the nebulization protocol, it resulted in a much higher titer suspension. The nebulizer produced a polydisperse aerosol; conversely, the electrospray produced a relatively monodisperse aerosol with a count peak at the mobility size of the single virion. The nebulized aerosol particle count was 2.8 times as variable as the electrosprayed aerosol particle count although neither aerosolization method maintained a constant count over repeated 15-minute filter tests. No differences in filter penetration were observed between nebulized and electrosprayed MS2 aerosol particles. Electrosprayed dextrose particles, used as an inert aerosol particle comparator, exhibited higher penetration than MS2 particles in two of the three filter samples, which can be attributed, at least partially, to the difference in dielectric properties of dextrose and virus particles. Both aerosolization methods generated culturable MS2 virions with the electrospray producing an airborne concentration approximately 20-fold higher than the nebulizer. In general, the electrospray produced cleaner, more stable, and more viable bacteriophage aerosol particles compared to conventional nebulization. The findings of this study are expected to assist researchers in selecting appropriate generation methods when using viable virus-based challenge aerosol particles.

Inactivation of Aerosolized Viruses in Continuous Air Flow with Axial Heating

“…In addition, the data points representing viruses in liquid may signify individual dispersed MS2 virions. In contrast, the MS2 aerosols generated by the Collison nebulizer are likely contained aggregates and/or particles covered by residue from the nebulization suspension (Eninger et al 2009;Hogan et al 2005;Riemenschneider et al 2010). These factors, in principle, can enhance resistance of aerosolized viruses to environmental stress, including heat.…”

Investigation of Antimicrobial Activity of Grapefruit Seed Extract and Its Application to Air Filters with Comparison to Propolis and Shiitake

“…The aerosol deposition method on antimicrobial filters has been performed in many other studies (Eninger et al, 2009;Jung et al, 2011b;Miaśkiewicz-Peska and Łebkowska, 2011). Two natural product extracts, GSE and propolis, were diluted with 95% ethanol (Samchun Pure Chemical Ind.…”

Method for Studying Survival of Airborne Viable Microorganisms in Combustion Environments: Development and Evaluation

“…The bioaerosol generation protocol has previously been validated and used in several studies (Mainelis et al, 1999;Lin et al, 2000;Grinshpun et al, 2005Grinshpun et al, , 2007. Alternatively, several other methods can be utilized for generating biological particles (Reponen et al, 1997;Ulevicius et al, 1997;Eninger et al, 2009;Jung et al, 2009c). The bioaerosol is diluted with HEPA-filtered dry air at different flow rates, which enables testing different flow regimes and different exposure times.…”