Microbiological aspects of ethylene oxide sterilization. IV. Influence of thickness of polyethylene film on the sporicidal activity of ethylene oxide.

Spores of Bacillus subtilis var. niger, dried on nonhygroscopic and hygroscopic surfaces, were enclosed in one of four thicknesses of low-density polyethylene film (2, 4, 6, and 20 mils). The surfaces were then placed in a specially designed thermochemical death rate apparatus and exposed to an ethylene oxide concentration of 600 mg/liter (at 54.4 C) and 50% relative humidity. Survival data, including both spore survivor curves and decimal reduction values (expressed as D values at 54.4 C-600 mg of ethylene oxide per liter), demonstrated similar survivor patterns when the B. subtilis var. niger spores were enclosed in low-density polyethylene films 2, 4, and 6 mils thick. A comparison of these patterns with those of spores enclosed in glassine and subjected to identical exposure conditions revealed only slight variations. The use of 20-mil polyethylene film greatly increased the time required to kill B. subtilis var. niger spores under the exposure conditions.