Preservation of Microorganisms by Freeze-drying: II. The Destructive Action of Oxygen. Additional Stabilizers for Serratia marcescens. Experiments with Other Microorganisms.

Ethylene oxide (ETO) in the form, "Cryoxcide,"' is used to sterilize surfaces and objects that cannot be treated with heat or corrosive chemicals. Cryoxcide is a gaseous formulation consisting of 11 per cent of ethylene oxide, 44.5 per cent of trichloromonofluoromethane (Freon 11), and 44.5 per cent of dichlorodifluoromethane (Freon 12). Cryoxcide is used at this laboratory to sterilize sensitive equipment that might be contaminated with foot-and-mouth disease virus. Sterilization was performed in the following manner. The contaminated equipment was placed in a gas autoclave at 78 F for 30 min at 40 per cent relative humidity. Cryoxcide was admitted into the chamber to a pressure of 11 lb per sq in. and the equipment was maintained for a 5-hr exposure under these conditions. An office calculating machine from a contaminated