Date Published: 3 August 2005

New cleaning process developed to cut hospital risk of CJD

Scientists at Edinburgh University in Scotland have developed a new technique that can rid surgical instruments of the infectious agents called prions that cause Creutzfeldt-Jakob Disease (CJD) in humans. The process is significant because prions are intrinsically different from all other viral and bacterial infections and remarkably difficult to remove by standard decontamination processes. Scientists working across five disciplines - chemistry, biomedicine, medicine, physics and engineering - are involved in the Department of Health funded project, which could soon be developed commercially.

The new technique can remove contaminating biomolecules from stainless steel surfaces to levels a thousand times lower than those achieved by existing methods. The process leaves no visible trace of any residual contaminated material. The technique, which is reported in the August 2005 edition of the Journal of General Virology, can also destroy the prions which cause scrapie in sheep and BSE in cattle.

Edinburgh scientists have used high energy forms of gas called plasmas to strip contaminating biomolecules from stainless steel surfaces. Gas-plasma cleaning involves using radio waves to excite the molecules of harmless gases. The excited molecules, and the charged atoms called ions and radicals formed in the process, effectively scour the surface of the instruments, breaking down traces of biological tissue and converting them to non-toxic gases. The process has been verified through a collaborative study with scientists from the Moredun Research Institute, Midlothian.

Studies have shown that the standards of surgical instrument cleaning and sterilisation in British hospitals vary considerably. Although the Department of Health has drawn up decontamination procedures for instruments that may have been exposed to the CJD prion, it is recognised that the guidelines are unlikely to remove all traces of infectivity. Developing new methods for destroying prions is therefore of vital importance.

CJD is the commonest form of human prion disease, and comprises a group of disorders including sporadic CJD and variant CJD (which is linked to BSE). All forms of CJD are progressive neurological disorders which are fatal and for which there is no cure. In the UK, there are between 50 and 65 deaths each year from sporadic CJD and, so far, there have been more than 150 deaths from variant CJD. It is not known how many people are incubating the disease.

Unlike other forms of CJD, in variant CJD the prion is widely distributed in lymphoid tissues in the body in addition to the central nervous system, raising concerns that the agent may be transmitted by contaminated surgical instruments used on lymphoid tissues - for example, the spleen or tonsils - and possibly by blood transfusion. CJD has occasionally been transmitted by contaminated neurosurgical instruments, tissue grafts, including corneal and dura mater grafts, and contaminated human pituitary hormones.

Professor Robert Baxter, of the University of Edinburgh's School of Chemistry, said:

"This new technique is significant because, unlike viral and bacterial pathogens, prions are proteins which are resistant to high temperatures and adhere very strongly to metal surfaces. Our integrated strategy aims to provide a new approach to decontamination of surgical instruments and to ensure that decontamination is effective."

Source: Edinburgh University, Scotland.

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