Submicronic Fungal Bioaerosols: High-Resolution Microscopic Characterization and Quantification

Submicronic particles released from fungal cultures have been suggested to be additional sources of personal exposure in mold-contaminated buildings.In vitro generation of these particles has been studied with particle counters, eventually supplemented by autofluorescence, that recognize fragments by size and discriminate biotic from abiotic particles. However, the fungal origin of submicronic particles remains unclear. In this study, submicronic fungal particles derived fromAspergillus fumigatus ,A. versicolor , andPenicillium chrysogenum cultures grown on agar and gypsum board were aerosolized and enumerated using field emission scanning electron microscopy (FESEM). A novel bioaerosol generator and a fungal spores source strength tester were compared at 12 and 20 liters min−1 airflow. The overall median numbers of aerosolized submicronic particles were 2 × 105 cm−2 , 2.6 × 103 cm−2 , and 0.9 × 103 cm−2 forA. fumigatus ,A. versicolor , andP. chrysogenum , respectively.A. fumigatus released significantly (P < 0.001) more particles thanA. versicolor andP. chrysogenum . The ratios of submicronic fragments to larger particles, regardless of media type, were 1:3, 5:1, and 1:2 forA. fumigatus ,A. versicolor , andP. chrysogenum , respectively. Spore fragments identified by the presence of rodlets amounted to 13%, 2%, and 0% of the submicronic particles released fromA. fumigatus ,A. versicolor , andP. chrysogenum , respectively. Submicronic particles with and without rodlets were also aerosolized from cultures grown on cellophane-covered media, indirectly confirming their fungal origin. Both hyphae and conidia could fragment into submicronic particles and aerosolizein vitro . These findings further highlight the potential contribution of fungal fragments to personal fungal exposure.