What do spore particles look like - use of real-time measurements and holography imaging to view spore particles from four bioaerosol generators

To study bioaerosols under controlled conditions, aerosol chambers equipped with aerosol generators have been used for a long time. The method used for generation can change the constitutionand properties of the bioaerosol produced, including the viability of fungal spores, bacteria or airborne viruses. The properties of a bioaerosol in turn influence the results of detection and enumeration methods downstream. To evaluate and compare bioaerosol generators, previous methods provided either real-time data without particle characterization, relied on labor-intensive microscopy or used culturing, which has high variability. In our study, we used the novel instrument SwisensPoleno Jupiter, providing real-time enumeration and subsequent bioaerosols characterization through holographic image analysis. With this tool, we investigated the characteristics of bioaerosols produced by four different aerosol generators using fungal spores from Aspergillus brasiliensis, Cladosporium cladosporioides and Trichoderma longibrachiatum in controlled chamber environments. The rotating brush generator (RBG) produce small, round particles for A. brasiliensis, between 5 and 15 µm, while the fungal aerosol generator (FAG) released small particles for C. cladosporioides and T. longibrachiatum. Conversely, the SwisensAtomizer (SWA) produced larger non-spheric particles, likely spore aggregates, and the liquid sparging aerosolizer (LSA), exhibited a high portion of datapoints with empty images, supposedly water droplets. All generators showed a wide range of particle sizes. Holographic image analysis revealed that the choice of bioaerosol generator had a significant influence on the constitutionof produced aerosols, in terms of proportions of single spores, chains and agglomerates, emphasizing the importance to select the bioaerosol generator depending on the desired aerosol.