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Inactivation of viable stress-resistant microorganisms using novel treatments

Nakpan, Worrawit
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552399176535309

Abstract Details

2019, PhD, University of Cincinnati, Medicine: Industrial Hygiene (Environmental Health).
The primary objective of this dissertation was to evaluate the inactivation performance of newly-developed reactive materials against microorganisms. The challenge biological agent used in this study was Bacillus thuringiensis var kurstaki (Btk bacterial spores), a non-pathogenic simulant of Bacillus anthracis (B.a.), which is a well-known bio-warfare agent. An air-acetylene flame and the combustion products of the reactive materials were utilized for the inactivation of the aerosolized spores. The effects of several factors such as time of exposure, material components, and proximity to the flame were evaluated. This effort was followed by an additional study focused on the inactivation of stress-resistant viable spores of Btk and Aspergillus fumigatus collected on ventilation filters by a combination of ultraviolet (UV) irradiation and the gaseous iodine treatment. In Study A (Chapter 1), the survival of aerosolized bacterial spores in a close proximity to a flame was investigated under test conditions relevant to a fire or explosion in a bio-weapon facility. Aerosolized spores of Btk were tested. The results of their exposure to two particle-to-flame proximity levels of an air-acetylene flame were obtained for different exposure time intervals ranging from ~0.1 to ~6.0 s. The study revealed that at relatively short time intervals, the inactivation values exponentially increased. However, as the exposure time increased, the loss of spore viability slowed down for both proximity levels. The study results pointed to the presence of “super-resistant” Btk spores, which was verified by a separate experiment. The findings justify a growing effort to synthesize special materials with pronounced biocidal capabilities and incorporate these into conventional weapons in order to achieve higher inactivation of the “super-resistant” bio-agents in the battlefield – the key objective of the US Department of Defense agent defeat program. Study B is a follow-up study that aimed at establishing an association between the spore inactivation caused by exposure to combustion products of different recently-developed materials and the exposure time. Powders of Al, Al·I2, Al·B·I2, Mg, Mg·S, and Mg·B·I2 were combusted, and viable aerosolized endospores of Btk were exposed to the released products for relatively short time periods: from ~0.1 to ~2.0 s. The tests were performed at two temperatures in the exposure chamber: ~170ºC and ~260ºC. The higher temperature and exposure times above 0.33 s generated distinctively higher inactivation levels (as high as ~105) for iodine-containing materials such as Al·I2, Al·B·I2, and Mg·B·I2 compared to other materials. In Study C, we investigated the inactivation of Btk and A. fumigatus spores collected on different filter materials due to various combinations of UV irradiation and the treatment by gaseous iodine. The study revealed that this combination is rather potent in an effort to reduce the spore viability. The sequence of application of UV and iodine matters; e.g., the UV irradiation followed by the iodine treatment exhibited significantly higher inactivation compared to that generated by the opposite sequence or simultaneous application. The physical factors associated with the filter structure can affect the inactivation of Btk spores, but these are not as influential for A. fumigatus spores.
Sergey Grinshpun, Ph.D. (Committee Chair)
Nancy Burton, Ph.D. (Committee Member)
Roman Jandarov, Ph.D. (Committee Member)
Tiina Reponen, Ph.D. (Committee Member)
88 p.
Environmental Health
Bioaerosol; Inactivation; Combustion; Flame; Filters

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Citations

  • Nakpan, W. (2019). Inactivation of viable stress-resistant microorganisms using novel treatments [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552399176535309

    APA Style (7th edition)

  • Nakpan, Worrawit. Inactivation of viable stress-resistant microorganisms using novel treatments. 2019. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552399176535309.

    MLA Style (8th edition)

  • Nakpan, Worrawit. "Inactivation of viable stress-resistant microorganisms using novel treatments." Doctoral dissertation, University of Cincinnati, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552399176535309

    Chicago Manual of Style (17th edition)

ucin1552399176535309
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This open access ETD is published by University of Cincinnati and OhioLINK.