Biological Indicators for the Control of Ethylene Oxide Sterilization

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Abstract
A new biological indicator was developed for the control of ethylene oxide sterilization, particularly for large scale sterilization of disposable medical equipment. The aim was to provide the new indicator with the same resistance to the combined effect of ethylene oxide and water vapor as the biological indicator referred to be the health authorities in Scandinavia. The reference indicator contains spores of a Danish test strain, Bacillus subtilis, in sand. The new one contains spores of a test strain used extensively for biological indicators, were exposed to ethylene oxide and water vapor in 5 different series of experiments and almost the same resistance was found. In simulated routine sterilization procedures, the new indicator was placed at locations not easily accessible for the gas and water vapor, and the results reflected the blockage of diffusion. The experiments included samples of household dust. The resistance of the microorganisms in the dust was compared with that of the biological indicators. Based on these comparisons, it is concluded that the resistance of the 2 biological indicators to ethylene oxide is in accordance with the official Scandinavian standard for sterilized medical equipment when used in the control of sterilization of products with low microbial contamination.