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disinfection has always been a liquidchemical disinfection only now morecommonly with peracetic acid rather than thealdehyde-based disinfectants that used to beprevalent. Peracetic acid, which works byoxidising bacterial components, filled the gapin the market as Glutaraldehyde was phasedout in the UK - mainly due to protein fixationand concerns regarding health effects.After disinfection it is equally important to

ensure that bacteria are not reintroduced orallowed to proliferate. After all, theendoscope is not guaranteed to becompletely free of bacteria.

Evolving technologies in decontamination

Preventing protein dryingStarting almost immediately after patientuse, the ‘bedside clean’ is now arecommended part of the process andensures the decontamination process beginsas early as possible. This presents animportant opportunity for development andimprovements to the process.One of the most important aspects of

soiling removal is to not allow the protein todry as it becomes more difficult to removeafterwards. Reprocessing the endoscopewithin three hours of patient use has beenthe traditional means of preventing dried onsoiling but this can be impractical or difficultto achieve - especially when procedures arehappening out-of-hours or at a locationremote from the procedure.3 A means ofprolonging this time-window is tosupplement the humidity of the endoscopes’environment, so as to slow the dryingprocess; increasing the relative humidityaround the soiling will decrease the rate ofevaporation. This can be achieved after thebedside clean with sealed transport bags anda moisture source, such as a wetted pad.The result will be an endoscope that is moreeasily cleanable and a much lesser challengeto the decontamination process. The process of transporting dirty

endoscopes is yet to be fully standardisedand there are many unanswered questions,such as: the effect of temperature; themaximum time where bacterial proliferationmay become an issue; and how well thehumidity will be maintained in theendoscope channels. To date, the latter issuehas not being given enough attention as theendoscope channels are much harder todecontaminate than the surface. This wholetransport process is largely unmonitoredwhich is an area for future technologies to

Since the early days of the ‘HTM 2030’Department of Health guidance document in1997, the process of decontaminating anendoscope has gone through significantchanges fuelled by a demand for a faster,safer process that suits the requirements ofthe modern healthcare system. EndoscopeWasher Disinfectors (EWDs) have had tokeep pace with the increasing complexity ofthe devices and so too have the testing andvalidation requirements in order to ensurepatient safety and reduce the risk of cross-contamination. There have been many recent innovations

such as capsule videoendoscopy and singleuse colonoscopes1 and these, along withother technologies, may in the future replacethe traditional flexible endoscope. For nowautomated high-level disinfection of thesereusable instruments remains the mosteconomical and rapid means to meet theever-increasing demand for diagnosticprocedures in the NHS.To achieve high-level disinfection, it is

critical that items are clean ie: free of proteinand organic matter. Many recentdevelopments have focused not on thedisinfection process but rather ensuringthorough cleaning takes places beforehand.2

The disinfection process itself has notchanged significantly and contains the basiccore components: wash; rinse; high-leveldisinfect; and final rinse. The high-level

David Woods BSc (Hons) has been the operations manager for T.E.S.T. since2014 and is an Authorised Person (Decontamination). Since university David has worked as a microbiologist and managed sterilisation and washer-disinfectorvalidation processes as part of the range of independent services offered by thecompany. Here, David examines some of the technologies being used to preservethe disinfected state of the endoscope - and also those being employed before the disinfection to ensure a successful and efficacious process.

Starting almost immediately after patient use, the‘bedside clean’ is now a recommended part ofthe process and ensures the decontaminationprocess begins as early as possible.

The flexible endoscopedecontamination cycle has alwaysretained the same key steps

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be developed to provide further assurancethat drying has been avoided, especiallywhere extended transport distances andtimes are being used.The bedside clean may also present some

additional risk to operators as liquids thathave a high level of potential pathogens arebeing generated and handled. A way tomitigate this risk and aid thedecontamination processes may be tointroduce a low-level non-toxic disinfectant tothe bed-side process and provide a ‘pre-disinfection’ as well as a pre-clean.

Improving the manual clean processThe only stage where the channels will bemechanically brushed is during the manualclean, hence it is a critical stage in theprocess. Carried out in a pre-cleaning sink,the manual clean with a sponge or lint-freecloth and flexible brush removes the majorityof the organic contamination from thechannels and outside of the endoscope. Thechannels must be flushed with a detergentsolution as the lumen will be too long andcomplex to be cleaned simply bysubmersion. Manual processes, althoughpotentially very effective, can vary fromoperator to operator so these are aided byautomated flushing systems. These oftenwall-mounted units deliver pump-drivendetergent to the channels to deliver aconsistent and controlled cleaning action.As is the case with any accessories, care

should be taken to follow all manufacturers’disinfection instructions for the flushingequipment itself as equipment could act as areservoir for bacteria and create additional risks- and a challenge for the disinfection process.

Delivering water to the endoscopewasher disinfectorSince the introduction of automatedmachines for disinfection of endoscopesthere have been recognised issues withcontamination,4 most notably in the finalrinse water.5 Filtration below 0.45 micron or0.2 micron had always been the traditionalway to ensure bacteria-free water and thismay have worked well under laboratoryconditions with single use equipment. Intheory, the pore sizes of the filters werenarrower than the smallest known bacteria.However, in practice, delivering consistentquality water over a long time-period with acomplex water system network would beunachievable without further treatment.Furthermore, it has been discovered thatthere may be more species than previouslythought that can pass through these filtersincluding Spirochaete and Actinobacteria

phyla.6 Biofilms of multiple species canquickly take hold of treatment equipment,pipework and the EWD itself and becomeextremely difficult to remove.Many different treatment methods have

evolved to tackle these issues, the currentguidance lists six recommended methods7: l Softeningl Deionisation l Distillationl Reverse osmosisl Filtrationl Disinfectant addition.

None of these technologies are new. However,allowing for ‘disinfectant addition’ is a recentchange in the Health Technical Memorandaand, as a result, there are new technologies tomeet this new recommendation. Someproducts are combining these technologies forinstance reverse osmosis (RO) purificationwith low level chlorine dioxide dosing toprevent bacterial proliferation within and afterthe filter.Although it may be quite straightforward

to filter water, it is more difficult to maintainthis bacteria-free state though a long networkof pipes and valves before it eventually entersthe endoscope. Low doses of non-toxicdisinfectant appear to be an important wayforward to ensure the water microbiological

quality is maintained in all areas the rinsewater travels though. Technologies such asthese fill a gap in the water treatmentprocess where only more limited single-pointtechnologies, such as ultraviolet, existedbefore.The traditional idea of aiming for

increasing purity of rinse water is beingchallenged as it is recognised that more thanone method is needed to maintain andensure patient safety. The current UKguidance states that even the traditionaltrusted indicator of water quality, electricalconductivity, is not important if biocides arepresent. As long as patient safety can bedemonstrated, residual biocide can lowerpotential infection risks as bacteria proliferatein standard final rinse water.

Going mobile The requirement for endoscopy in the NHShas massively increased in recent years due,in part, to programmes such as the NHSBowel Cancer Screening Programme(BCSP).8 To meet the required targets andreduce procedure waiting times hospitals areturning to mobile endoscopy suites withbuilt-in decontamination facilities. This ismuch more cost effective compared toredevelopment and rebuilding, which maytake years to complete. These often privatelyrun trailer type units are equipped with thefull range of decontamination equipmentincluding manual cleaning sinks, washer-disinfectors and drying cabinets. Such self-supporting systems can include the patienttreatment rooms, recovery wards andconsulting rooms. Although a stop-gapsolution, some of these units offer a fullycompliant process and can have faster turn-

Example of an ISO 15883-4 compliant surrogate device used to test endoscope drying cabinets

The decontamination process still follows the familiar basic steps but will look very different from the processes and equipment 20 years ago.

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around compared to transport to anotherhospital. Decontamination units in the future will

undoubtedly change further still as thedemands for an adaptable and cost-efficientsolution increase.

The ‘use-by’ dateTo cut costs and waste, the shelf-life of theprocessed endoscope is being extended byvarious products and technologies.Decontamination units no longer need to putthe disinfected endoscope back into thewasher after three hours because of concernsof bacterial growth; the endoscopes may bedried and packed in a preserved state.Drying cabinets have been around for a

decade or more and evolved from theendoscope storage cupboards of-old to createa system that actively dries and maintainsthe internal and external microbial quality foroften up to 30 days. These were neverdescribed in the original HTM 2030document and only in 2015 aninternational standard became officiallyavailable to dictate their design and testingrequirements.9 The principle of the storageaspect is similar to what people consider tobe a ‘cleanroom’ environment with positivepressure and HEPA filtration. Drying canhelp to reduce the risk of biofilmdeveloping inside the endoscope as thedesiccation will prevent the formation orgrowth of biofilms from anymicroorganisms that remain. In some situations, where the patient

need is not immediate, or perhaps furtherafield, transport of the processedendoscope is necessary. Endoscopepacking systems have become increasinglycommonplace, mostly due to the statedmaximum storage time which may savecosts in reprocessing due to expiring thetraditional three hour time window. As inthe early days of drying cabinets, theinternational standards are not yetdeveloped to fully cover their use andtesting, therefore we see a variety ofsystems and methods on the market. Various gases, liquids and vacuum

methods are employed in this area topreserve and protect the state of theendoscope after drying. But, without fullydefined testing and validation standards,users can be left without independentreassurance. Users should seek advicefrom their Authorising Engineer forDecontamination before putting suchequipment into use.With these additional stages being

added to the process it is more importantthan ever that all the links in thedecontamination ‘chain’ are secure. Each step is reliant on the previous stages being effective and validatedotherwise the whole process will fall apartand potentially endanger patient safety.Storage methods cannot by their nature‘disinfect’, only maintain the state hencethey are reliant on highly disinfected and

dry endoscopes as a starting point. The complexity and number of steps in

the process means that staff are more relianton tracking systems to work out the ‘where,when, who and how’.

Traceability - following the stepsEndoscope tracking and traceability has beenone of the areas that would not have beenpossible with the computer systems from 20years ago. Now a unit manager has theability to instantly assess where anendoscope has been reprocessed, all patientsit was ever used on and its current location.This is a critical tool for infection control ifpatients need to be recalled due to faultyequipment or processes and makestraceability fast and more straight-forwardthan paper-based systems.

A new definition for ‘clean’Testing methods for EWDs have beenadapted over the years to accommodate the

practical difficulties of maintaining andmanaging a high-level disinfection processfor endoscopes. A lot of the tests described inthe 1997 memorandum were based aroundpharmaceutical specifications that weresimply not achievable using treated mainstap water. Users who were not able to stickto the strict specifications were left in thedark because the guidance lacked anyinterpretation for bacterial and endotoxinlevels and no advice on remediation wasgiven. Specifications for test methods,particularly microbiological tests, are lessprescriptive and more advisory, putting theonus back to the end-user to risk-assess anddecide the best outcomes for the patients,infection control and budgets.Final rinse water microbiological counts

are carried out weekly and now allowed upto 10 cfu (Colony Forming Units) per 100mLwith colour coded guidance and action levelsbeyond this. The endotoxin maximum limit isnow 120x higher than previous guidance

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and the chemical purity specifications havebeen removed and rely on drinking waterspecifications. When taking into consideration that most

flexible endoscopy procedures are notperformed in a sterile cavity and theendoscope retains very little residual rinsewater, the justifications for these changesbecome apparent. Compared to otherdecontamination processes such as steamsterilisation, EWDs have seen the mostchanges in their testing and standards inrecent years. The quality of testing is vital,users should ensure samples are sent toUKAS accredited testing laboratories forassurance of quality management and toensure methods are validated and carried outby proficient laboratory staff.One area that has received a lot of

attention in recent years is residual proteinafter reprocessing. Not specific to endoscopybut for all medical instruments, the ADCP-TSE subgroup determined that currentprotein detection methods were not sensitiveenough and highlighted a requirement fornew technologies to reliably and quantifiablydetect to the microgram level. This hasspurred suppliers to produce a new range ofprotein detection products and tests, none ofwhich are yet standardised in the guidance.Despite revisions to the testing methods,

improvements EWD design and othertechnological innovations, studies are beingreleased indicating that biofilms withinflexible endoscopes are still a cause forconcern.10 Disinfectant resistant biofilms mayneed routine, intensive treatment fromalternative chemistry as they build upresistance from the routine processes. Thedirection of development of the endoscopealways tends to be focused in the diagnosticand imaging direction, whereasconsiderations of disinfection and cleaninghave received little attention.

Is sterilisation the answer?Due to the nature of the design and materialcompatibility, the endoscope cannot besimply steam sterilised and must go throughlow temperature processes. High-leveldisinfection is not enough assurance for somesensitive procedures and endoscope types,such as choledochoscopes. In these cases,sterilisation is required either by plasma (LowTemperature Hydrogen Peroxide) or ethyleneoxide. These sterilisation methods are neveras fast as automated washer disinfectors,some of which can complete in less than 20minutes. Sterilisation usually requiresdegassing over the course of several hoursand the sterile barrier system needs to be

maintained through any transport process.Faster sterilisation technologies willundoubtedly become available in the nearfuture and potentially all flexible endoscopescould be sterilised. Protein removal in thewashing stages will always need to be animportant step in the processing of reusableinstruments, therefore sterilisation can neverbe the panacea for all problems indecontamination.In conclusion, the decontamination

process still follows the familiar basic stepsbut will look very different from the processesand equipment 20 years ago. Proteinremoval and disinfection will be moreeffective thanks to recent innovation andtechnologies. Our greater understanding of the chemical

and biological aspects of the process isconstantly changing how we define andmonitor the whole system. The pace of changeis increasingly rapid and testing and validationrequirements are yet to be fully defined forsome areas, so it is now more important thanever for users to seek advice and verify.Complacency with endoscope decontaminationrisks endangering patients so we must activelyprepare and anticipate risks. CSJ

References1. Medlatest (2016). URL:

https://www.medlatest.com/specialty/endoscopy/ce-mark-worlds-sterile-single-use-endoscope-colonoscopies

2. British Society of Gastroenterology (2017).Guidance for decontamination for gastrointestinalendoscopy

3. ADCP-TSE Subgroup (2015). General principles ofdecontamination and waste disposal URL:https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/427855/Annex_C_v3.0.pdf

4. Alvardo et al. (1991). Nosocomial infections fromcontaminated endoscopes: A flawed automatedendoscope washer. An investigation using molecularepidemiology. American Journal of Medicine

5. Cook et al. (1998) Bacteria-free water for automaticwasher-disinfectors: an impossible dream? Journal of Hospital Infection

6. Hahn (2004) Broad diversity of viable bacteria in‘sterile’ (0.2 �m) filtered water. Research inMicrobiology

7. Department of Health (2016). Health TechnicalMemorandum 01-06: Decontamination of flexibleendoscopes: Part B – Design and installation.

8. Public Health England (2015). URL:https://www.gov.uk/guidance/bowel-cancer-screening-programme-overview

9. Technical Committee CEN/TC 102 (2015). BS EN16442 Controlled environment storage cabinet forprocessed thermolabile endoscopes. BritishStandards Institute

10. Akinbobola et al. (2017). Tolerance of Pseudomonasaeruginosa in in-vitro biofilms to high-levelperacetic acid disinfection. Journal of HospitalInfection

Testing for Environmental Mycobacteria in rinse water

Due to the nature of the design and materialcompatibility, the endoscope cannot be simply steam sterilised and must go through low temperature processes.