Decontamination of Surfaces Contaminated with Prions

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Decontamination of Surfaces Contaminated with
Prions

• Dr. Gerald McDonnell

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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

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Intrinsic Resistance

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

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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

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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

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Current Decontamination Methods

• Sodium hydroxide
• Device damage concerns
• Autoclave damage
• Safety concerns

Reprinted on request from Hotel Dieu Grace,
Windsor, Ontario
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Summary

• TSEs 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

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Decontamination Research

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

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In Vivo Methodology
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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)

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Positive Controls
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Wash-Off Controls
At 280 days incubation (gt9 months)
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Autoclave studies
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Cleaning Studies
Formulated for efficacy and compatibility on
medical devices and other surfaces
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Further Technologies
Previously published as effective in suspension
studies
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