Resistance of Spores of Clostridium botulinum 33A to Combinations of Ultraviolet and Gamma Rays1
- 1 January 1969
- journal article
- research article
- Published by American Society for Microbiology in Applied Microbiology
- Vol. 18 (1) , 44-50
- https://doi.org/10.1128/aem.18.1.44-50.1969
Abstract
Spores of Clostridium botulinum 33A exhibit a sigmoidal survival curve if subjected to gamma radiation. The present investigation was concerned with two questions: (i) what is the form of an ultraviolet (UV)-survival curve and (ii) what is the combined effect of UV- and gamma radiation? The UV-survival curve was found to be of sigmoidal type with a “shoulder” width of 675 ergs/mm2 and a D10 (exp) of 2,950 ergs/mm2. To test the combination effect, spores were subjected to UV doses of 225, 450, 675, and 900 ergs/mm2 followed by a series of increasing doses of gamma rays from 200 to 2,000 krad in 200-krad steps. The gamma ray-survival curves showed that increasing UV pretreatment caused a gradual loss of the “Prodiginine” yielding straight line exponential survival curves after preirradiation with UV doses of 675 ergs/mm2 and above. Simultaneously the D10 value for gamma-ray irradiation was reduced, e.g. UV preirradiation with 900 ergs/mm2 reduced the D10 by 40%. This observation emphasizes the potential practical advantage of combining UV and gamma rays for sterilization of heat-sensitive commodities.Keywords
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