Please use this identifier to cite or link to this item: https://hdl.handle.net/10356/83455
Title: Activation and inactivation of Bacillus pumilus spores by kiloelectron volt X-ray irradiation
Authors: Ha, Thi Mai Hoa
Yong, Derrick
Lee, Elizabeth Mei Yin
Kumar, Prathab
Lee, Yuan Kun
Zhou, Weibiao
Keywords: Bacillus
Bacterial spores
Issue Date: 2017
Source: Ha, T. M. H., Yong, D., Lee, E. M. Y., Kumar, P., Lee, Y. K., & Zhou, W. (2017). Activation and inactivation of Bacillus pumilus spores by kiloelectron volt X-ray irradiation. PLOS ONE, 12(5), e0177571-.
Series/Report no.: PLOS ONE
Abstract: In this study, we investigated the inactivation efficacy of endospore-forming bacteria, Bacillus pumilus, irradiated by low-energy X-rays of different beam qualities. The different low-energy X-rays studied had cut-off energies of 50, 100 and 150 keV. Bacillus pumilus spores (in biological indicator strips) were irradiated at step doses between 6.5 to 390 Gy. The resulting bacteria populations were then quantified by a pour plate method. Results showed that X-rays of lower energies were more effective in inactivating bacterial spores. In addition, an increment in bacterial population was observed at doses below 13Gy. We attributed this increase to a radiation-induced activation of bacterial spores. Four kinetic models were then evaluated for their prediction of bacterial spore behavior under irradiation. This included: (i) first-order kinetics model; (ii) Shull model; (iii) Sapru model; and (iv) probabilistic model. From R2 and AIC analyses, we noted that the probabilistic model performed the best, followed by the Sapru model. We highlighted that for simplicity in curve fitting the Sapru model should be used instead of the probabilistic model. A 12-log reduction in bacterial population (corresponding to a sterility assurance level of 10−6 as required in the sterilization of medical devices) was computed to be achievable at doses of 1000, 1600 and 2300 Gy for the three different X-ray cut-off energies respectively. These doses are an order in magnitude lesser than that required in gamma irradiation. This highlights the applicability of cheaper and safer table-top X-ray sources for sterilization application.
URI: https://hdl.handle.net/10356/83455
http://hdl.handle.net/10220/42640
ISSN: 1932-6203
DOI: 10.1371/journal.pone.0177571
Rights: © 2017 Ha et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Fulltext Permission: open
Fulltext Availability: With Fulltext
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