AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Ultraviolet Irradiation and Gaseous Iodine Treatments against Viable Bacterial and Fungal Spores Deposited on Air Filters
SERGEY A. GRINSHPUN, Worrawit Nakpan, Michael Yermakov, Reshmi Indugula, Tiina Reponen, University of Cincinnati
Abstract Number: 12 Working Group: Bioaerosols
Abstract Viable bacterial and fungal spores collected on air handling filters may re-aerosolize and represent a health risk. This problem has been recognized by the bio-defense and indoor air quality communities. Methods are being developed to control stress-resistant viable microorganisms on filters. In this study, we investigated the potential of ultraviolet (UV) irradiation and gaseous iodine treatments for inactivating spores of Bacillus thuringiensis var. kurstaki (Btk), a surrogate of B. anthracis, and Aspergillus fumigatus, a common opportunistic pathogen used as an indicator for indoor air quality. The spores were collected on HEPA and non-HEPA filters, both flattened for testing purposes, as well as on a mixed cellulose ester (MCE) membrane filter used as a reference. A commercial HEPA unit with a deep-bed (non-flattened) filter was also tested. Combined treatments with UV and iodine on MCE filter produced a significant synergy in inactivating Btk spores. However, no similar synergy was observed for A. fumigatus. For spores collected on an MCE filter, the inactivation effect was about an order of magnitude greater for Btk compared to A. fumigatus. The filter type was found to be an important factor affecting the inactivation of Btk spores while it was not as influential for A. fumigatus. Overall, the combined effect of UV irradiation and gaseous iodine demonstrated some potential for inactivating spores on air handling filters. Unfortunately, the benefit of either simultaneous or sequential treatment was much lower for Btk spores embedded inside the deep-bed (non-flattened) HEPA filter as compared to the flat ones. For A. fumigatus the inactivation on flattened and non-flattened HEPA filters was comparable. For both species, applying UV first and gaseous iodine second produced significantly higher inactivation than when applying them simultaneously or in an opposite sequence. The data interpretation involved the spore structure and stress-response mechanisms.