SPORICIDAL ACTION OF PERACETIC-ACID AND PROTECTIVE EFFECTS OF TRANSITION-METAL IONS

Although peracetic acid (PAA) is used widely for cold sterilization an d disinfection, its mechanisms of sporicidal action are poorly underst ood, PAA at high concentrations (5-10%) can cause major loss of optica l absorbance and microscopically-visible damage to bacterial spores, S pores killed by lower levels of PAA (0.02-0.05%) showed no visible dam age and remained refractile, Treatment of spores of Bacillus megateriu m ATCC 19213 with PAA at concentrations close to the lethal level sens itized the cells to subsequent heat killing. In addition, PAA was foun d to act in concert with hypochlorite and iodine to kill spores, Antio xidant sulfhydryl compounds or ascorbate protected spores against PAA killing, Trolox, a water-soluble form of cw-tocopherol, was somewhat p rotective, while other antioxidants, including a-tocopherol, urate, bi lirubin, ampicillin and ethanol were not protective, Chelators, includ ing dipicolinate, were not protective, but transition metal ions, espe cially the reduced forms (Co2+, Cu+ and Fe2+) were highly protective. The net conclusions are that organic radicals formed from PAA are spor icidal and that they may act as reducing agents for spores that are no rmally in a highly oxidized state, in addition to their well known act ions as oxidizing agents in causing damage to vegetative cells.