RADIATION‐RESISTANT MICRO‐ORGANISMS ISOLATED FROM TEXTILES

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Abstract
Towels from private homes and public offices and underwear contaminated by being used by employees at a public health laboratory were examined for occurrence of radiation-resistant bacteria and fungi. Three different methods were used for isolation of the most resistant organisms, 1 with multiplication of the microbial population prior to an irradiation used for selection and 2 without this multiplication and with the organisms placed on membrane filters or in situ on the textiles, respectively. A total of 44 different strains were isolated. Differences in the 3 methods used for selection of the most radiation-resistant microorganisms were not reflected in the results; 16 pigment-producing gram-positive cocci, tentatively classified as Micrococcus radiodurans, were the most radiation-resistant and were isolated in .apprx. 1/2 of the examinations. Other gram-positive cocci, non-spore forming rods, some Nocardia and Candida parapsilosis strains and 2 Bacillus strains constituted the rest of the collection. With few exceptions dose-response curves for the strains were upward convex. D-6 values were between 1.5 megarad for the most radiation-sensitive, a Candida, and were 5.7 megarad for the most resistant, tentatively classified as M. radiodurans. The D-6 values for the Bacillus strains were in both cases 1.8 megarad, consistent with a D-value of 0.3 megarad. The same resistance is the maximum resistance for B. pumilus, strain E601, commonly used as reference strain in the literature on radiation sterilization of medical devices and supplies.

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