Application of a fluorescent dual stain to assess decontamination of tissue protein and prion amyloid from surgical stainless steel during simulated washer-disinfector cycles

Summary Current World Health Organization guidelines pertaining to the reprocessing of surgical instruments in the face of potential iatrogenic transmission of Creutzfeldt–Jakob disease (iCJD) are incompatible for the vast majority of devices. This has led to the advent of a range of new decontamination measures. Even without the implementation of these new procedures, the incidence of proven iCJD through surgery remains low. In this study, existing decontamination processes in sterile service departments have been evaluated using simulated washer-disinfector cycles on surgical grade stainless steel wires inoculated with ME7 scrapie homogenate. The consequence of varying the soil drying times and choice of cycle pre-treatment on prion removal were evaluated. Assessment of residual contamination at each cycle phase was carried out with the application of a sensitive fluorescent staining procedure to identify both total protein and prion-associated amyloid. The study confirmed that immediate reprocessing following contamination was beneficial during the pre-treatment phase with either an enzymatic or pre-soak wetting agent. Final total protein levels at the end of the cycles, were not significantly different from those where the soil was allowed to dry. In addition, cycles involving a pre-treatment with either an enzymatic cleaner or pre-soak, whether the soil was allowed to dry or not, showed complete removal of detectable prion amyloid. The results suggest that current decontamination procedures, combined with immediate processing of surgical instruments, have the potential to be highly effective alone at reducing the risk of surgical transmission of CJD.