Resistance of spores of Clostridium botulinum 33A to combinations of ultraviolet and gamma rays.

Applied Microbiology
E Durban, N GRECZ

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/mm(2) and a D(10) (exp) of 2,950 ergs/mm(2). To test the combination effect, spores were subjected to UV doses of 225, 450, 675, and 900 ergs/mm(2) 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/mm(2) and above. Simultaneously the D(10) value for gamma-ray irradiation was reduced, e.g. UV preirradiation with 900 ergs/mm(2) reduced the D(10) by 40%. This observation emphasizes the potential practical advantage of combining UV and gamma rays for sterilization of heat-sensitive commodities.

References

Jul 15, 1962·Proceedings of the National Academy of Sciences of the United States of America·R B SETLOW, J K SETLOW
Oct 1, 1962·Physics in Medicine and Biology·S A TYLER, M H DIPERT
Jan 4, 1965·Biochemical and Biophysical Research Communications·P T EMMERSON, P HOWARD-FLANDERS
May 1, 1965·Applied Microbiology·A ANELLISD BERKOWITZ

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