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What is the procedure to discard the
specimens ordered for CJD e.g csf,urine,blood etc.
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Prions are resistant to most conventional inactivation procedures including irradiation, boiling, dry heat, and chemicals (formalin, betapropiolactone, alcohols). Prion infectivity in purified samples is reduced but not eliminated by prolonged digestion with proteases, boiling in sodium dodecyl sulfate and urea. Organic solvents such as phenol and chaotropic reagents such as guanidine isothiocyanate reduce but do not eliminate residual infectivity. In addition, standard autoclaving protocols do not inactivate prions completely.
The safest and most unambiguous method for ensuring that there is no risk of residual infectivity on contaminated instruments and specimens is to destroy them by incineration. (reference 1) Current recommendations for inactivation of prions on instruments and other materials are based on the use of sodium hypochlorite, NaOH and the moist heat of autoclaving with combinations of heat and chemical being most effective.
The following methods may be used to inactivate prions on reusable instruments and surfaces. (from reference 2).
1. Immerse in 1 N NaOH, and heat in a gravity displacement autoclave at 121oC for 30 minutes. Clean and sterilize by conventional means.
2. Immerse in 1 N NaOH or sodium hypochlorite (20,000 ppm) for 1 hour. Transfer into water and autoclave (gravity displacement) at 121oC for 1 hour. Clean and sterilize by conventional means.
3. Immerse in 1N NaOH or sodium hypochlorite (20,000 ppm) for 1 hour. Rinse instruments with water, transfer to open pan and autoclave at 121oC (gravity displacement) or 134oC (porous load) for 1 hour. Clean and sterilize by conventional means.
4. Surfaces or heat-sensitive instruments can be treated with 2N NaOH or sodium hypochlorite (20,000 ppm) for 1 hour. Ensure surfaces remain wet for entire time period, then rinse well with water. Before chemical treatment, it is strongly recommended that gross contamination of surfaces be reduced because the presence of excess organic material will reduce the strength of either NaOH or sodium hypochlorite solutions.
1. World Health Organization. [http://www.who.int/en/]. Geneva (Switzerland): The Organization; [updated 2006 Sept 21; cited 2006 Sept 21]. 2000. WHO Infection Control Guidelines for Transmissible Spongiform Encephalopathies. Report of a WHO Consultation, Geneva, Switzerland, 23-26 March 1999. [about 2 screens]. Available from: http://www.who.int/csr/resources/publications/bse/WHO_CDS_CSR_APH_2000_3/en/
2. Centers for Disease Control and Prevention. 2007. Biosafety in Microbiological and Biomedical Laboratories. US Government Printing Office, Washington, DC. Available at: http://www.cdc.gov/od/ohs/biosfty/bmbl5/bmbl5toc.htm
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