Decontamination of Surfaces Contaminated with Prions Dr. Gerald McDonnell

Iatrogenic prion transmission Human tissues and contaminated surfaces can transmit TSEs Human tissue examples Medical device examples Experimental evidence Zobeley et al, 2001 ‘Prions are readily and tightly bound to stainless steel surfaces and can transmit scrapie to recipient mice after short implant exposure times’

Intrinsic Resistance Prions demonstrate resistance to routine methods of decontamination and sterilization Prions are proteins, not microorganisms

Current Decontamination Methods Cleaning Can cleaners increase or decrease the risk? Physical removal Lipophilic soil Environmental fate Which cleaners should/should not be recommended? Aldehyde-based cleaners should be contra-indicated Use of alkaline cleaners

Current Decontamination Methods Steam sterilization Data in the literature conflicting ‘Steam sterilization alone is NOT effective’ Higher sterilization temperatures may be less effective Published reports of survival following gravity displacement autoclaving Ernst & Race(1993): 132C/ 1 hour Taylor (2000): 134C/ 1 hour

Current Decontamination Methods Sodium hydroxide Device damage concerns Autoclave damage Safety concerns Reprinted on request from Hotel Dieu Grace, Windsor, Ontario

Summary TSE’s can be transferred via medical devices and other surfaces Current recommended decontamination methods need to be verified and validated Priocidal, compatibility, safety Alternative decontamination technologies? High and low temperature

Decontamination Research Test Methodology Method Development Method Validation Decontamination Methodology Existing recommended methods Developing technologies

In Vivo Methodology

Study design TSE Strain: Scrapie 263K Test animal: Syrian hamsters Test device: stainless steel wires Test inoculum 10% brain homogenate, 1 hour Dried 16 hours, room temperature 14 control groups (12 animals) Positive controls (LD 50 ), diluted in ‘negative’ brain homogenate Negative controls Wash-off controls Decontamination methods (12 animals/group)

Positive Controls

Wash-Off Controls DilutionMean Mortality (Days)* No RinseRinse in PBS (15 mins) 3rd th *At 280 days incubation (>9 months)

Autoclave studies MethodMean Death (days) ‘Log’ Reduction Porous Load Autoclave 134 o C, 18 minutes ~150~4 Porous Load Autoclave 134 o C, 18 minutes (immersed in water) TBD>6 Enzymatic cleaner+ Gravity drain autoclave (121 o C, 20 mins) ~250~6

Cleaning Studies MethodMean Death (days) ‘Log’ Reduction Formulated* Enzymatic Cleaner ~145~4 Formulated* Alkaline Cleaner TBD>6 Enzymatic cleaner+ Gravity drain autoclave (121 o C, 20 mins) ~250~6 *Formulated for efficacy and compatibility on medical devices and other surfaces

Further Technologies MethodMean Death (days) ‘Log’ Reduction Phenolic disinfectant* (5%, 30 mins) TBD>6 Formulated Oxidizing Agent (12 mins) ~145~4 NaOH (1N, 1 hour) TBD>6 *Previously published as effective in suspension studies