Μανδραλή Θωμαίς, Ιατρός, Ωτορινολαρυγγολόγος, Βέροια, Ημαθίας

The major transmissible spongiform encephalopathies (TSEs) of humans include Creutzfeldt–Jakob disease (CJD), kuru, fatal familial insomnia, Gerstmann–Strussler–Scheinker syndrome, and, within the past 10 years, variant CJD (vCJD). The pathology of these neurodegenerative diseases of the central nervous system is associated with the presence of pathologic prions, an abnormal conformation of a normal cellular protein [1].

Prions have been shown to be highly resistant to sterilisation procedures. Bernoulli et al in 1977 described a cerebral depth electrode that was used in a patient who subsequently developed CJD [2].; Following sterilisation in benzene and alcohol, the elec­trode was used on two further patients who also later developed CJD. The same electrode was again sterilised and implanted into the brain of a chimpanzee which later developed a spongiform encephalopathy. More recently, Zobelcy et al confirmed by mouse models that steel instruments can retain CJD infectivity even after formaldehyde treatment [3]. Infectivity of prions persists even after autoclaving at conventional temperatures and time periods (121 C for 15 minutes) and demonstrates extreme resis­tance to high doses of ionising and UV radiation.[4]

Τhe ability of preparations of enzymatic medical instrument cleaners to reduce the infectivity associated with a rodent-adapted strain of human prion disease, previously reported to be resistant to decontamination, was tested. Efficient degradation of the disease-associated prion protein by enzymatic cleaning preparations required high treatment temperatures (50-60 degrees C).

Standard decontamination methods (1 M NaOH for 1 h or autoclaving at 134 degrees C for 18 min) reduced infectivity associated with the human-derived prion strain by less than 3 log10 LD50. In contrast, a 30 min treatment with the optimized enzymatic cleaning preparation protocols reduced infectivity by more than 3 log10 LD50 and when used in conjunction with autoclave cycles eliminated detectable levels of infectivity. The development of prion decontamination procedures that are compatible with routine cleaning and sterilization of medical and surgical instruments may reduce the risk of the transmission of prion disease in general surgery[3].

References

1. Sehulster LM. Prion inactivation and medical instrument reprocessing: challenges facing healthcare facilities. Infect Control Hosp Epidemiol. 2004 Apr;25(4):276-9 Comment on:

Infect Control Hosp Epidemiol. 2004 Apr;25(4):280-3. 2. Bernoulli C, Siegfried J, Baumgartner G, Regli F, Rabinowicz T, Gajdusek DC, Gibbs CJ Jr. Danger of accidental person-to-person transmission of Creutzfeldt-Jakob disease by surgery. Lancet. 1977 Feb 26;1(8009):478-9.

3. Zobeley E, Flechsig E, Cozzio A, Enari M, Weissmann C. Infectivity of scrapie prions bound to a stainless steel surface. Mol Med. 1999 Apr;5(4):240-3. Comment in:  Mol Med. 1999 Oct;5(10):701.

4. Advisory Committee on Dangerous Pathogens Spongiform Encephalopathy Agents. Safe working and the Prevention of infection. 1998. London. The stationary office.

5. Lawson VA, Stewart JD, Masters CL. Enzymatic detergent treatment protocol that reduces protease-resistant prion protein load and infectivity from surgical-steel monofilaments contaminated with a human-derived prion strain. J Gen Virol. 2007 Oct;88(Pt 10):2905-14