© Georg Thieme Verlag KG Stuttgart · New York
Safe storage of endoscopes: change in our guidelines?
17 August 2007 (online)
Endoscopes are complex instruments used in body areas that are extremely well colonized by microbes. For this reason, intensive contamination of endoscopes by microorganisms - both pathogenic and nonpathogenic - and other organic substances from the gastrointestinal tract is unavoidable . Additionally, endoscopes are exposed during use to extreme mechanical stresses, first during the investigation procedure itself and then during the subsequent reprocessing. Unavoidable damage to the internal surfaces can promote the adherence of microorganisms and the substances mentioned above.
A further point is the fact that reprocessing in general takes place in an environment that is free from germs, but not under aseptic conditions. Recontamination can therefore be avoided only when the instruments are finally sterilized and stored sealed in the sterile condition. This is necessary only when an instrument is to be used later in body areas that are primarily free of germs.
The risk of germ transmission during endoscopic procedures is influenced by three factors:
The internal surfaces of an endoscope should be of a quality such that mechanical stress can cause only small injuries. Microorganisms and organic substances from the gastrointestinal tract can then adhere in only small amounts. Additionally, the construction of the endoscope must allow cleaning and disinfection fluids to reach all contaminated areas - because at each reprocessing these fluids can be effective only where they can reach 2. Cleaning and disinfection procedures must be sufficiently effective. Manual reprocessing procedures can be as effective as mechanical procedures if defined procedure steps are carried out precisely. Mechanical procedures have the advantage of standardization 3. Regular microbiological checks of reprocessing efficacy are essential. In addition to the quality of the result, the quality of the process needs to be evaluated as well 4. Reprocessed endoscopes must be stored between endoscopic procedures in such a way that neither recontamination with pathogenic germs nor growth of remaining microorganisms is possible 5.
It is common sense that each of these factors depends on the previous one. However effective the cleaning and disinfection fluids, they can only rinse germs out of the channels if they can reach all internal surfaces in sufficient volume and at sufficient pressure. Multiplication of pathogenic microorganisms during endoscope storage can be ruled out only if the organisms have been eliminated during the preceding reprocessing. Secure storage of reprocessed endoscopes is absolutely necessary to ensure good hygiene in endoscopy, and it is irritating that in a German metropolitan area - even 2 years after publication of clear recommendations  - 10 % of private endoscopy centers continue to store reprocessed endoscopes inappropriately . Nevertheless, even appropriate storage cannot prevent transmission of infectious agents after ineffective or undereffective reprocessing.
Using safely reprocessable endoscopes, the reprocessing with effective procedures and appropriate storage until next use must be considered as a unit. The most important element is the effective reprocessing, because in an endoscope that is free of germs, pathogenic microorganisms that do not exist cannot multiply and therefore cannot pose a risk. Basically, it must be required that every single step of the reprocessing follows evidence-based criteria. In reality, enormous discrepancies may be observed in regard to actual practice at various endoscopic centers . Individual reprocessing procedures may be effective, but are not necessarily so. Following evidence-based guidelines, on the other hand, gives the user security that the endoscopes are being stored free of germs or only insignificantly contaminated with nonpathogenic microorganisms. Rejchrt et al.  were able to demonstrate the absence of germs in the channels of 135 endoscopes that underwent manual cleaning and high-level mechanical disinfection, even after 5 days of storage. Only a few instruments were externally contaminated with skin-derived germs. In the present issue of Endoscopy Osborne et al. present similar results. Of course, over a period of 7 days an average of 15.5 % of endoscopes were contaminated with nonpathogenic germs. After 5 days a yeast was detected in only one case. However, the contamination rate did not increase in the long run.
Indicators that it is possible to use effectively reprocessed endoscopes in patients after several days’ storage without additional reprocessing are increasing. The current US  and German  recommendations do not contain this demand, but do require the following of evidence-based reprocessing steps that are described in detail, with effective drying of channels. In contrast to this, the ESGE guidelines  include the requirement to disinfect the endoscopes before every session. However, these guidelines relate to predominantly manual reprocessing procedures and describe the reprocessing steps only roughly and not in an evidence-based manner.
Knowledge about the reprocessing of endoscopes, the use of washer-disinfectors and the implementation of recommendations have improved in recent years. With additional results from further microbiological studies on effective reprocessing and storage, the European guidelines, too, may be changed.
Competing interests: None
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M. Pietsch, , MD
Department of Hygiene and Environmental Medicine
University of Mainz
Hochhaus am Augustusplatz