Radiation resistance of Candida parapsilosis

The radiation resistance of 30 strains classified as Candida parapsilosis was examined. The strains originated partly from environments where ionizing radiation was used for research or routine purposes, partly from environments with no known possibility for selection of strains with unusually high radiation resistance. D-6 values between 1.5 and 2.4 Megarads were found when the cells were irradiated in the dried state, a D-6 value being the dose necessary to reduce the initial number of colony-forming units with a factor of 10(6). The majority of D-6 values were between 1.9 adn 2.1 Megarads. D-6 values for the cells irradiated in liquid media were about 2/3 of those in the dried state. No difference in resistance was revealed depending on the origin of the strains examined For radiation sterilization of medical products the demonstrated resistance of Candida parapsilosis might be of importance if routine use of minimum doses below 2.5 Megarads were to be accepted.