Endoscope reprocessing – painted into a corner?

The inherent issue of reusable complex instruments – such as flexible endoscopes – being incompatible with heat-based sterilization has been recognized for decades, prompting ever-developing guidelines for optimal reprocessing [1] [2]. High level disinfection (HLD) is an integral part of quality endoscopy, which combined with appropriate manual cleaning and drying/storage has been thought to offer a satisfactory safeguard against retained contamination and potential microbial transmission between patients. Indeed, most reported endoscope-transmitted infections used to be linked to technical failures or lack of adherence to reprocessing standards.

Thus, the recent reports on infectious outbreaks in the context of appropriate reprocessing have been particularly disturbing [3] [4] [5] and the topic has gained renewed significance. A well-documented incident in the US, where transmission was linked to the mechanical construction of duodenoscope elevators [6] [7] sparked a long-needed discussion on the adequacy of current guidelines, particularly so because the micro-organisms in question were partially multidrug-resistant “superbugs” with potentially devastating clinical effects.

In the current issue of Endoscopy, Hervé & Keevil report on another, more general issue of endoscope reprocessing: the risk of residual contamination in the channels of endoscopes [8]. They acquired end-of-life endoscopes as well as new endoscope channels and studied contamination and the effect of standard and extended reprocessing, using sophisticated detection methods (fluorescence epimicroscopy). The background to the study was at least partly the concern for prion transmission via endoscopes, in particular the risk of Creutzfeldt – Jakob disease [9]. While no case of endoscope-associated prion transmission with clinical consequences has been reported, the prevalence of asymptomatic carriers of the disease gives reason for concern. In this respect the presence of biofilm and protein deposits, particularly amyloid protein, is important, because these residues greatly facilitate harboring of prions and other hard-to-destroy organisms.

The findings in the present report add to the concerns about endoscope reprocessing. Even in brand-new channels, standard HLD was unable to clear all the protein residues. Moreover, the amount of residues increased significantly with the wear and tear of daily use, probably because of the microdamage inflicted on the channels with usage and cleansing. This study was not aimed at microorganisms per se, thus, the clinical significance of the findings is unknown. However, the presence of protein residues definitely increases the risk of microbial contamination and growth, and perhaps more importantly, the study shows that existing reprocessing methods are unable to remove all particulate matter within our endoscopes. Also, while this paper focuses on channel residues, the contamination of other endoscope components (e. g. the duodenoscope elevator), the endoscope storage, and the mechanical cleaning may also play a significant role in the overall results of endoscope reprocessing.

So, where does this leave us?

The most significant outcome of the present situation is awareness that endoscope reprocessing is a critical component of quality gastrointestinal endoscopy, and that it is presently suboptimal, thus calling for improvement. A number of elements in the current procedures might conceivably be addressed in such an improvement process.

First and foremost, all HLD is rendered useless if the manual cleansing is incomplete [2]. Thus, fail-safe mechanical cleaning routines must be enforced and audited on a regular basis, adhering to published guidelines and endoscope manufacturer recommendations.

Second, the advent of further improved and more effective disinfection agents seems likely. An achievable step already available would be to limit the use of glutaraldehyde, which is known to facilitate the development of biofilm in addition to the other health issues related to its usage [10]. Sterilization with ethylene oxide has been suggested [11], but the efficacy has been questioned, and the cost and practicality of this approach makes it a less attractive alternative at present time [12].

Routine quality control of endoscope reprocessing by testing post-reprocessing cleanliness is a valid approach and should be implemented in all clinical units. However, the process of accurate sampling and culturing of channel flushing fluid is not trivial, and it has been advised that this should not be handled “in-house.” There is a risk that false-negative sampling routines and failure to pick up potentially important positive cultures may engender a false sense of security [12].

Following investigations into the Seattle outbreak, the design of the duodenoscope was a focus of attention. Specifically, the mechanism of the elevator and the elevator wire channel were identified as potential culprits. As a result, an extensive program was initiated on the part of Olympus to service all duodenoscopes with replacement of the O-ring by a higher quality version. In the same effort, additional attention was given to the specifics of mechanical cleaning of the endoscope tip. Of note, similar issues with the elevator channel have been reported with all popular brands of duodenoscopes. Thus, it is likely that the present situation will spark research and development efforts to provide instruments that facilitate more effective reprocessing. Conceivably, parts of the instruments – or even the endoscope itself – might be replaced by single-use components, but this would need to happen without loss of functionality.

Finally, the issue of endoscope-based cross-infection must be put into perspective. Gastrointestinal endoscopy is not a risk-free activity, and we accept a certain prevalence of morbidity and even mortality, given the obvious benefits offered by our endoscopes. The overall worldwide number of reports on scope infection outbreaks remains low. Despite the present and highly welcome efforts to improve on reprocessing, it is likely that for a long time to come we will have to accept that completely bug-free instruments remain an illusion. Although quality assurance is an obvious component of our daily work, we must avoid painting ourselves into a corner, creating quality requirements that render critically important endoscopic activity impractical or even illegal.

• References

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