The sterilisation or cleaning of medical instruments has been a hot topic in the press over the past few months: first, the revelation that poorly cleaned duodenoscopes were behind a deadly superbug outbreak in some US healthcare facilities, and second, the discovery of a new prion – a variant of the misfolded proteins associated with incurable progressive brain diseases such Creutzfeldt-Jakob Disease (CJD) – which also appears to be transmissible from animal to animal.
In view of the findings about the duodenoscopes, the US Food and Drug Administration (FDA) has produced a new standard that requires duodenoscope cleaning to eliminate all but 6.4mcg/cm2 of protein. In addition, the FDA has switched to the inoculum used in British testing, thought to be tougher to clean than the previously used artificial test soil (ATS).
The second headline is about new research by scientists from the University of California at San Francisco (UCSF), which suggests that a newly discovered type of prion – alpha-synuclein – may be the cause of a progressive neurodegenerative disorder know as Multiple System Atrophy (MSA), which has similarities to Parkinson’s disease.
The paper’s lead author, Stanley Prusiner – who won the Nobel prize in 1997 for his discovery that CJD could be transmitted by a misfolded protein – suggests that this new disease is also potentially infectious.
MSA in its early stages is frequently misdiagnosed as Parkinson’s disease, which is often treated with deep-brain stimulation equipment. If this equipment is re-used, even with standard sterilisation protocols in place, there is the potential for the disease to be transmitted to other patients.
Standard disinfection techniques that kill microbes do not eliminate the prions that cause CJD, and so special cleaning methods are required. Proteins prove difficult to remove from instruments but new fluid dynamic washing technologies are currently being tested in the US that may help, so watch this space.