decontamination of surfaces contaminated with prions dr. gerald mcdonnell
TRANSCRIPT
Decontamination of Surfaces Contaminated with Prions
Dr. Gerald McDonnell
Iatrogenic prion transmission
Human tissues and contaminated surfaces can transmit TSEsHuman tissue examplesMedical device examples
Experimental evidenceZobeley 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
CleaningCan cleaners increase or decrease the risk?
Physical removalLipophilic soil
Environmental fateWhich cleaners should/should not be
recommended?Aldehyde-based cleaners should be contra-indicatedUse of alkaline cleaners
Current Decontamination Methods
Steam sterilizationData in the literature conflicting‘Steam sterilization alone is NOT effective’Higher sterilization temperatures may be
less effectivePublished reports of survival following gravity
displacement autoclavingErnst & Race(1993): 132C/ 1 hourTaylor (2000): 134C/ 1 hour
Current Decontamination Methods
Sodium hydroxideDevice damage
concernsAutoclave damageSafety 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 validatedPriocidal, compatibility, safety
Alternative decontamination technologies? High and low temperature
Decontamination Research
Test Methodology Method DevelopmentMethod Validation
Decontamination Methodology Existing recommended methodsDeveloping technologies
In Vivo Methodology
In Vivo Methodology
Study designTSE Strain: Scrapie 263KTest animal: Syrian hamstersTest device: stainless steel wiresTest inoculum
10% brain homogenate, 1 hourDried 16 hours, room temperature
14 control groups (12 animals)Positive controls (LD50), diluted in ‘negative’ brain homogenateNegative controlsWash-off controls
Decontamination methods (12 animals/group)
Positive Controls
50
7090
110130
150
170190
210
0 1 2 3 4 5 6 7
Serial Dilution (Positive Control)
Mo
rta
lity
(D
ay
s)
Wash-Off Controls
Dilution Mean Mortality (Days)*
No Rinse Rinse in PBS
(15 mins)
3rd 108 113
5th 169 165
*At 280 days incubation (>9 months)
Autoclave studies
Method Mean Death
(days)
‘Log’ Reduction
Porous Load Autoclave
134oC, 18 minutes
~150 ~4
Porous Load Autoclave 134oC, 18 minutes
(immersed in water)
TBD >6
Enzymatic cleaner+ Gravity drain autoclave
(121oC, 20 mins)
~250 ~6
Cleaning Studies
Method Mean Death
(days)
‘Log’ Reduction
Formulated*
Enzymatic Cleaner
~145 ~4
Formulated*
Alkaline Cleaner
TBD >6
Enzymatic cleaner+ Gravity drain autoclave
(121oC, 20 mins)
~250 ~6
*Formulated for efficacy and compatibility on medical devices and other surfaces
Further Technologies
Method Mean 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
