1. Decontamination of Surfaces Contaminated with Prions Dr. Gerald McDonnell

2. 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’

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

4. 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

5. 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

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

7. 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

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

9. In Vivo Methodology

10. 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 (LD50), diluted in ‘negative’ brain homogenate • Negative controls • Wash-off controls • Decontamination methods (12 animals/group)

11. Positive Controls

12. Wash-Off Controls *At 280 days incubation (>9 months)

13. Autoclave studies

14. Cleaning Studies *Formulated for efficacy and compatibility on medical devices and other surfaces

15. Further Technologies *Previously published as effective in suspension studies