# Presentation: 429830

## 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

## 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

| 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

## Slide 16