Rapid enzymatic test system for the overall process efficacy of automated washer-disinfector processes for thermolabile endoscopes

Author: Markus Wehrl*, Amelie Achten


Background: Process challenge devices (PCDs) according to Annex 9 of the Guideline are used for the process control of the overall reprocessing efficacy for thermolabile endoscopes. The analysis of these PCDs is sophisticated and requires a microbiological laboratory. These PCDs are therefore not appropriate for routine controls in central sterile departments.

Material and methods: Within a research project, a PCD system was developed that is simple and fast to use for the routine control of the overall process efficacy of processes that rely on glutaraldehyde as isinfectant. The system is based on special enzymes immobilized on a fibrin matrix in tubeshaped devices. The enzymes selected act as surrogates for the conventional test organisms (Enterococcus faecium), as the enzymes are equivalently denatured by process-typical temperatures and concentrations of the disinfectant.

Results: Comparative investigations in the laboratory as well as in hospitals demonstrated the good match of results between the new enzymatic test system and PCDs according to Annex 9.


Due to the complex structure and the use of thermolabile materials, flexible endoscopes are regarded as difficult to reprocess. The reprocessing of these “semi-critical B” instruments includes cleaning according to the KRINKO/BfArM recommendations [1], following the manufacturer’s reprocessing instructions, and chemical or chemothermal disinfection. According to Paragraph 8, Sentence 1 of the German Medical Devices Operator Ordinance [2], validated reprocessing is required to ensure that a successful outcome is guaranteed and traceable and that the safety and health of patients, users or third parties is not jeopardized. The validation of automated washer-disinfector processes for thermolabile endoscopes (WD-E) can be carried out, for example, in accordance with the Guideline of DGKH, DEGEA, DGSV, DGVS and AKI together with manufacturers of endoscopes and endoscope WDs [3]. In addition to numerous other tests, the following tests – which are directly relevant to the endoscope reprocessing result – are carried out within the framework of the performance qualification (PQ):

  • Cleaning efficacy – Process control – Annex 8 of the Guideline [4]
  • Overall reprocessing efficacy – Process control – Annex 9 of the Guideline [5]
  • Overall reprocessing efficacy – Final- product control – Annex 10 of the Guideline [6]

Final-product controls, such as the microbiological contamination control on or in prepared real instruments (endoscopes contaminated by real use) described in Annex 10, are important quality control adjuncts, but they remain limited to fixed sample numbers. They do not allow quantitative measurement of the reprocessing efficacy, only a classification along the lines of “pass/fail”. Process controls are of great importance for the quantitative assessment of the efficacy of a process, as a comprehensive assessment of the basic reprocessing efficacy strictly requires the use of well-defined process challenging devices (PCDs)....

Read more in Steri-World Issue 01/2018.

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