Prions Flashcards
Prions should be handled as CL3 organisms
How are they transported to lab?
Transport as Category B (UN3373)
What is first aid if prion material gets on open wound?
Scrub with warm soapy water
Which of these decontamination measures are effective?
Aldehyde
Chlorine dioxide
Ethylene dioxide
Hypochlorite
Sodium Hydroxide
Phenol
Autoclave
Ionising radiation
Incineration
Prions when dry adhere very strongly to surfaces. Important to keep cleaning area damp/ moist
Effective:
Sodium Hydroxide - effective but irritant
Phenol - most effective but very destructive
Incineration - needs to be >850degC
Ineffective:
Aldehyde
Chlorine dioxide
Ethylene dioxide
Hypochlorite - partially effective, but very toxic
Autoclave - reduce risk, but don’t eliminate
Ionising radiation
In the cleaning of surgical instruments by Department of Health ACDP, what is upper limit of protein detection on surfaces?
5 micrograms/ side of instrument
lower for neurosurgical instruments which will be in contact with high risk tissues
thought that less protein, suggests better cleaning, and less risk of prior transmission in those who prion disease is not suspected
if patient suspected of having prion disease, their instruments should be isolated from use from others
Who is at risk of hereditary CJD?
Familial CJD is a very rare genetic condition where one of the genes a person inherits from their parent (the prion protein gene) carries a mutation that causes prions to form in their brain during adulthood, triggering the symptoms of CJD
Blood relative with known mutation
At least two blood relatives with compatible syndrome
Who is at risk of variant CJD?
caused by consuming meat that had bovine spongiform encephalopathy
younger people
consuming meat that has had bovine spongiform encephalopathy
Or
risk from others who already have vCJD:
surgery with instruments from either confirmed case OR at risk individual
Received organs or tissue from confirmed case OR at risk individual
Donor of blood to someone who then developed vCJD
Receiver of blood from donor who then developed vCJD
Receiver of blood from donor who also gave to someone who then developed vCJD
Plasma products pre-2001
Who is at risk of sporadic CJD?
Most common type
Due to misfolding protein appearing sometime between age 45-75
Random mutation causing prior disease
Or
iatrogenic:
Pituitary
hormones pre-1985 in UK, perhaps more recently overseas
Neurosurgical procedures pre-1992 with possibility of dura mater
graft
Use of any instruments that used on someone who then developed CJD
Corneal grafts
Blood with white cells, protein component -
now sourced outside UK for children
CJD Tissue grading
What tissues are considered high risk?
High risk
CNS tissue
Posterior eye tissue
Pituitary tissue
CJD Tissue grading
What tissues are considered medium risk?
spinal ganglia
Olfactory epithelium
Lymphoid tissue - gut lymph tissue, spleen, Thymus, appendix, tonsils
adrenals
CJD Tissue grading
What tissues are considered low risk?
Every other tissue which is not high or medium risk
Patient with confirmed or possible CJD
How are surgical instruments disposed/ cleaned?
High/ medium risk -
- destroy - incinerate
- quarantine - if to be used again
- try and use single use instruments as much as possible
Low risk
- normal process, but good audit trail needed
Patient with confirmed or possible CJD
What are the steps of quarantining instruments
Keep instruments separate during procedure
Wash instruments well - cover in damp cloth
normal sterilisation process
put in sealed box - either for re-use on same patient of destruction
If diagnosis confirmed as CJD - destroy instruments
If alternative diagnosis found - can bring out of quarantine
If die before diagnosis - destroy instruments
