Sporicidal Activity of an Improved Iodide Formulation and Suggestions Regarding the Biological Safety Cabinet

The sporicidal activity of an improved iodide formulation based on a previously reported agent (Kida et al., 2004, tentatively designated as the KMT reagent) which is composed of 50 mM EDTA-2Na, 50 mM ferric chloride hexahydrate (FeCl3·6H2O), 50 mM potassium iodide (KI) and 50% ethanol in 0.85% NaCl solution at pH 0.3 with hydrochloric acid, was examined in the liquid and vapor phases. The improved iodide formulation subject to distillation (tentatively designated as the distilled KMT reagent: pH around 3) showed comparable sporicidal activity with the KMT reagent. As for the dilution effect, dilution at 1:2 showed more potent sporicidal activity than the undiluted one. It achieved complete disinfection with a treatment for 5 min at 20°C and for 60 min at 5°C. Even at a ratio of 1:100, the dilutions showed significant sporicidal activities at 37°C. The experiment on the disinfection of the biological safety cabinet (Class II type A) as a practical possibility showed that pretreatment with 400 ml of water vapor treatment, and a mixture of 300 ml of this reagent and 150 ml of water in vapor phase achieved complete disinfection after a 24 h-decontamination process. The distilled KMT reagent may be useful for disinfecting against various contaminated materials and sites in both the liquid phase and vapor phase.