Resistance of Clostridium sporogenes Spores to Radiation and Heat in Various Nonaqueous Suspension Media

Abstract

The influence of suspension in a phosphate buffer and various lipid media on the heat and radiation resistance of Clostridium sporogenes PA3679 was examined. Lyophilized spores were suspended in vegetable oils, animal fats, synthetic triglycerides, glycerol, or phosphate buffer, and their radiation and heat D]0 values (dose or time required for 90% inactivation) were determined. Radiation D10 values in the lipids were much higher than in the phosphate buffer. Radiation D10 values in glycerol and animal fats were higher than in the vegetable oils and the synthetic triglycerides. The D10 values in triolein and tributyrin were close to each other, suggesting that chain length may not be a significant factor in radiation resistance. The heat D10 value of the spores in a phosphate buffer at 95 ± 1°C was close to that in beef fat and was much higher than in any of the other lipid media tested. The heat D10 value in triolein was greater than twice that in tributyrin, suggesting that the fatty acid chain length is an important factor in the heat resistance of the spores in triglycerides. The effects of various nonaqueous suspension media on the radiation-induced thermosensitivity of spores were also determined. A comparison of the heat D10 values of the spores with and without prior irradiation in various media showed that irradiation at 5.0 kGy greatly increased their heat sensitivity.