Endoscope Washer-disinfectors Research Articles

Is ultraviolet light disinfection fit to be the future standard for the disinfection of flexible endoscopes without a working channel?

To investigate colony-forming unit (CFU) reduction on contaminated flexible endoscopes (FEs) without a working channel after UV-C light disinfection, compared to the current disinfection method with the endoscope washer disinfector (EWD). After pharyngolaryngoscopy, a manual pre-cleaning with tap water was performed. A culture was then collected by rolling the distal 8-10 cm of the FE over an Agar plate. The FE was disinfected using the D60 (60-s disinfection process with UV-C light) or the EWD (gold standard reprocessing process with water and chemicals). Another culture was then taken. After incubation, a CFU count was performed. A total of 200 FEs without a working channel were divided equally between the two disinfection groups. After clinical use and manual pre-cleaning, 84 of the 100 (84.0%) (UV-C light group) and 79 of the 100 (79.0%) (EWD) FEs were contaminated with at least 1 CFU. FEs that showed no contamination after use were excluded from further analysis. After disinfection with UV-C light, 72 (85.7%) FEs showed no contamination (i.e., 0 CFUs) versus 66 (83.5%) FEs after reprocessing with the EWD. There is no difference in CFUs reduction on contaminated FEs without a working channel between UV-C light disinfection and the current gold standard, the EWD.

Bacillus subtilis NDmed, a model strain for biofilm genetic studies

The Bacillus subtilis strain NDmed was isolated from an endoscope washer-disinfector in a medical environment. NDmed can form complex macrocolonies with highly wrinkled architectural structures on solid medium. In static liquid culture, it produces thick pellicles at the interface with air as well as remarkable highly protruding ‘‘beanstalk-like’’ submerged biofilm structures at the solid surface. Since these mucoid submerged structures are hyper-resistant to biocides, NDmed has the ability to protect pathogens embedded in mixed-species biofilms by sheltering them from the action of these agents. Additionally, this non-domesticated and highly biofilm forming strain has the propensity of being genetically manipulated. Due to all these properties, the NDmed strain becomes a valuable model for the study of B. subtilis biofilms. This review focuses on several studies performed with NDmed that have highlighted the sophisticated genetic dynamics at play during B. subtilis biofilm formation. Further studies in project using modern molecular tools of advanced technologies with this strain, will allow to deepen our knowledge on the emerging properties of multicellular bacterial life.

A pseudo-outbreak of Rhinocladiella similis in a bronchoscopy unit of a tertiary care teaching hospital in London, United Kingdom.

Outbreaks of fungal infections due to emerging and rare species are increasingly reported in healthcare settings. We investigated a pseudo-outbreak of Rhinocladiella similis in a bronchoscopy unit of a tertiary care teaching hospital in London, UK. We aimed to determine route of healthcare-associated transmission and prevent additional infections. From July 2018 through February 2019, we detected a pseudo-outbreak of R.similis isolated from bronchoalveolar lavage (BAL) fluid samples collected from nine patients who had undergone bronchoscopy in a multispecialty teaching hospital, during a period of 8months. Isolates were identified by MALDI-TOF mass spectrometry. Antifungal susceptibility testing was performed by EUCAST broth microdilution. To determine genetic relatedness among R.similis isolates, we undertook amplified fragment length polymorphism analysis. To determine the potential source of contamination, an epidemiological investigation was carried out. We reviewed patient records retrospectively and audited steps taken during bronchoscopy as well as the subsequent cleaning and decontamination procedures. Fungal cultures were performed on samples collected from bronchoscopes and automated endoscope washer-disinfector systems. No patient was found to have an infection due to R.similis either before or after bronchoscopy. One bronchoscope was identified to be used among all affected patients with positive fungal cultures. Physical damage was found in the index bronchoscope; however, no fungus was recovered after sampling of the affected scope or the rinse water of automated endoscope washer-disinfectors. Use of the scope was halted, and, during the following 12-month period, Rhinocladiella species were not isolated from any BAL specimen. All pseudo-outbreak isolates were identified as R.similis with high genetic relatedness (>90% similarity) on ALFP analysis. The study emphasises the emergence of a rare and uncommon black yeast R.similis, with reduced susceptibility to echinocandins, in a bronchoscope-related pseudo-outbreak with a potential water-related reservoir. Our findings highlight the importance of prolonged fungal culture and species-level identification of melanised yeasts isolated from bronchoscopy samples. Possibility of healthcare-associated transmission should be considered when R.similis is involved in clinical microbiology samples.

Endoscope decontamination: making the guidance work in practice

Endoscope decontamination prevents cross-infection and misdiagnosis. Legislation and guidance exist to ensure this, and Joint Advisory Group (JAG) accreditation is dependent on correct adherence. Due to their cost and complex construction, endoscopes have to be decontaminated between patients. Manual cleaning is an integral part of the decontamination process and helps ensure prions, which can transmit Creutzfeldt-Jakob disease (CJD), are cleared. Guidelines and standards include Medicines and Healthcare products Regulatory Agency (MHRA) Top Ten Tips, British Society of Gastroenterology (BSG) guidance, Department of Health and Social Care (DHSC) advice and the health technical memorandum, MTH-01-06. Over recent years, guidance has been updated. Changes incorporate tracking and traceability, levels of essential practice and best practice requirements, time from bedside clean to endoscope washer disinfection processing and issues around CJD. Guidance includes following the manual decontamination process, use of endoscope washer disinfectors, choice of disinfectants, rinse-water quality, safety, endoscope storage, operational management, environmental design and training. By following the most up-to-date guidance and legislation, nurses can ensure the safety of both patients and staff.

Occupational asthma caused by peracetic acid-hydrogen peroxide mixture.

Healthcare practice in the UK has moved away from using aldehyde disinfectants for the decontamination of endoscopes, in part due to the risk of respiratory sensitization. Peracetic acid (PAA) in combination with hydrogen peroxide (HP) is a commonly used alternative. We describe a case of occupational asthma (OA) diagnosed at our specialist occupational lung disease clinic and caused by occupational exposure to PAA-HP mixture, used as a disinfectant in an endoscope washer-disinfector machine. A 48-year-old man employed as a mycologist and environmental microbiologist at a Birmingham city hospital, UK, presented following an acute exposure to PAA-HP mixture causing lacrimation, burning optic pain and headache. He had also experienced symptoms suggestive of OA for the preceding 10 months, and the diagnosis was confirmed through OASYS analysis of serial peak expiratory flow measurements. He had been exposed to PAA-HP mixture whilst working in the endoscopy department for 12 months prior to the acute episode, and a subsequent specific inhalation challenge test was positive with a late asthmatic response to PAA-HP mixture. This case provides evidence for a sensitization mechanism in OA caused by PAA-HP mixture.

ESGE-ESGENA technical specification for process validation and routine testing of endoscope reprocessing in washer-disinfectors according to EN ISO 15883, parts 1, 4, and ISO/TS 15883-5.

1 Prerequisites. The clinical service provider should obtain confirmation from the endoscope washer-disinfector (EWD) manufacturer that all endoscopes intended to be used can be reprocessed in the EWD. 2 Installation qualification. This can be performed by different parties but national guidelines should define who has the responsibilities, taking into account legal requirements. 3 Operational qualification. This should include parametric tests to verify that the EWD is working according to its specifications. 4 Performance qualification. Testing of cleaning performance, microbiological testing of routinely used endoscopes, and the quality of the final rinse water should be considered in all local guidelines. The extent of these tests depends on local requirements. According to the results of type testing performed during EWD development, other parameters can be tested if local regulatory authorities accept this. Chemical residues on endoscope surfaces should be searched for, if acceptable test methods are available. 5 Routine inspections. National guidelines should consider both technical and performance criteria. Individual risk analyses performed in the validation and requalification processes are helpful for defining appropriate test frequencies for routine inspections.

Prevention of multidrug-resistant infections from contaminated duodenoscopes: Position Statement of the European Society of Gastrointestinal Endoscopy (ESGE) and European Society of Gastroenterology Nurses and Associates (ESGENA).

Patients should be informed about the benefits and risks of endoscopic retrograde cholangiopancreatography (ERCP)Only specially trained and competent personnel should carry out endoscope reprocessing.Manufacturers of duodenoscopes should provide detailed instructions on how to use and reprocess their equipment.In the case of modifications to their equipment, manufacturers should provide updated instructions for use.Detailed reprocessing protocols based on the manufacturer's instructions for use should clearly lay out the different reprocessing steps necessary for each endoscope model.Appropriate cleaning equipment should be used for duodenoscopes in compliance with the manufacturer's instructions for use. Only purpose-designed, endoscope type-specific, single-use cleaning brushes should be used, to ensure optimal cleaning. As soon as the endoscope is withdrawn from the patient, bedside cleaning should be performed, followed by leak testing, thorough manual cleaning steps, and automated reprocessing, in order to: · Remove debris from external and internal surfaces;. · Prevent any drying of body fluids, blood, or debris;. · Prevent any formation of biofilms.. In addition to the leak test, visual inspection of the distal end as well as regular maintenance of duodenoscopes should be performed according to the manufacturer's instructions for use, in order to detect any damage at an early stage.The entire reprocessing procedure in endoscope washer-disinfectors (EWDs) should be validated according to the European and International Standard, EN ISO 15883. Routine technical tests of EWDs should be performed according to the validation reports.Microbiological surveillance of a proportion of the department's endoscopes should be performed every 3months, with the requirement that all endoscopes used in the unit are tested at least once a year.In the case of suspected endoscopy-related infection, the relevant device (e. g., endoscope, EWD) should be taken out of service until adequate corrective actions have been taken. Outbreaks should be managed by a multidisciplinary team, including endoscopy, hygiene, and microbiology experts, manufacturers, and regulatory bodies, according to national standards and/or laws. In the case of suspected multidrug-resistant organism (MDRO) outbreaks, close cooperation between the endoscopy unit and the clinical health provider is essential (including infection control departments and hospital hygienists).

Tolerance of Pseudomonas aeruginosa in in-vitro biofilms to high-level peracetic acid disinfection

Biofilm has been suggested as a cause of disinfection failures in flexible endoscopes where no lapses in the decontamination procedure can be identified. To test this theory, the activity of peracetic acid, one of the widely used disinfectants in the reprocessing of flexible endoscopes, was evaluated against both planktonic and sessile communities of Pseudomonas aeruginosa. To investigate the ability of P.aeruginosa biofilm to survive high-level peracetic acid disinfection. The susceptibility of planktonic cells of P.aeruginosa and biofilms aged 24, 48, 96, and 192 h to peracetic acid was evaluated by estimating their viability using resazurin viability and plate count methods. The biomass of the P.aeruginosa biofilms was alsoquantified using Crystal Violet assay. Planktonic cells of P.aeruginosa were treated with 5-30 ppm concentration of peracetic acid in the presence of 3.0 g/L of bovine serum albumin (BSA) for 5 min. Biofilms of P.aeruginosa were also treated with various peracetic acid concentrations (100-3000 ppm) for 5 min. Planktonic cells of P.aeruginosa were eradicated by 20 ppm of peracetic acid, whereas biofilms showed an age-dependent tolerance to peracetic acid, and 96 h biofilm was only eradicated at peracetic acid concentration of 2500 ppm. Ninety-six-hour P.aeruginosa biofilm survives 5 min treatment with 2000 ppm of peracetic acid, which is the working concentration used in some endoscope washer-disinfectors. This implies that disinfection failure of flexible endoscopes might occur when biofilms build up in the lumens of endoscopes.

Risk-assessment-based approach to patients exposed to endoscopes contaminated with Pseudomonas spp.

Patients exposed to bronchoscopes contaminated with Pseudomonas aeruginosa are at increased risk of pseudomonal infection. The optimal methods for management and mitigation of risk following exposure are controversial. This article describes a two-phase risk assessment following pseudomonal contamination of a family of 75 endoscopes, detected through routine surveillance and attributed to one endoscope washer-disinfector. An initial risk assessment identified 18 endoscopes as high risk, based on the presence of lumens used for irrigation or biopsy. Exposure was communicated to the patients' clinical teams and a further clinical risk assessment of the exposed patients was performed. No patients developed complications due to pseudomonal infection.

Endoscopy supply water and final rinse testing: five years of experience

The penultimate stage in endoscope reprocessing is the final rinse with water following terminal disinfection. This requires a degree of microbiological and chemical control of the quality of the final rinse water. To report experience gained over five years of testing, reporting and managing the quality of final rinse water for endoscopic devices. Three endoscope reprocessing units, each comprising five endoscope washer-disinfectors (EWDs) supplied by two reverse osmosis (RO) water units, were subjected to weekly monitoring and control of final rinse water quality. EWDs were subjected to nightly thermal self-disinfection, and RO units were subjected to periodic sanitization with peracetic acid. Final rinse water samples were processed periodically for total viable counts (TVCs), Pseudomonas spp., endotoxins, conductivity, environmental mycobacteria and Legionella spp. Over the five-year study period (2008-2013), no Pseudomonas spp., environmental mycobacteria or Legionella spp. were isolated from endoscopy rinse water. All conductivity readings were below 30 μs/cm. Endotoxin levels fluctuated over the recommended cut-off of 0.25 EU/mL, with no correlation with TVCs. Trend analysis of TVCs established alert and action limits. Apart from the supply water of one EWD becoming contaminated with Aspergillus spp., there have been no interruptions to operational capacity of the endoscope reprocessing units. Quality control principles coupled with appropriate thermal and chemical disinfection of EWDs resulted in the achievement of microbiological standards for final rinse water. A co-ordinated team approach between the microbiology department, infection control department, endoscope unit managers and estates department is required to achieve this degree of success.

Biofilms of a Bacillus subtilis Hospital Isolate Protect Staphylococcus aureus from Biocide Action

The development of a biofilm constitutes a survival strategy by providing bacteria a protective environment safe from stresses such as microbicide action and can thus lead to important health-care problems. In this study, biofilm resistance of a Bacillus subtilis strain (called hereafter NDmedical) recently isolated from endoscope washer-disinfectors to peracetic acid was investigated and its ability to protect the pathogen Staphylococcus aureus in mixed biofilms was evaluated. Biocide action within Bacillus subtilis biofilms was visualised in real time using a non-invasive 4D confocal imaging method. The resistance of single species and mixed biofilms to peracetic acid was quantified using standard plate counting methods and their architecture was explored using confocal imaging and electronic microscopy. The results showed that the NDmedical strain demonstrates the ability to make very large amount of biofilm together with hyper-resistance to the concentration of PAA used in many formulations (3500 ppm). Evidences strongly suggest that the enhanced resistance of the NDmedical strain was related to the specific three-dimensional structure of the biofilm and the large amount of the extracellular matrix produced which can hinder the penetration of peracetic acid. When grown in mixed biofilm with Staphylococcus aureus, the NDmedical strain demonstrated the ability to protect the pathogen from PAA action, thus enabling its persistence in the environment. This work points out the ability of bacteria to adapt to an extremely hostile environment, and the necessity of considering multi-organism ecosystems instead of single species model to decipher the mechanisms of biofilm resistance to antimicrobials agents.

Resistance and cross-resistance to oxidising agents of bacterial isolates from endoscope washer disinfectors

Bacteria isolated from washer disinfectors using chlorine dioxide as a high-level disinfectant were exposed to peracetic acid, chlorine dioxide and hydrogen peroxide to investigate their susceptibility and possible bacterial cross-resistance to these highly reactive oxidising biocides. A standard suspension test was used to establish a rate of kill of these biocides against two stable isolates (Bacillus subtilis and Micrococcus luteus). Suspension tests demonstrated that 'in use' concentrations were not always effective to provide the required disinfection efficacy within recommended exposure times and in some instances a 60min exposure was necessary to achieve a reduction in number by a factor of 10(5). It appears that vegetative Gram-positive isolates can become resistant to oxidising agents in vitro, and that cross-resistance to related compounds can occur. Since these bacteria are deemed to be susceptible to highly reactive biocides, there should be further study of the resistance mechanisms in these isolates to explain their survival.

Follow-up and Management of Patients Exposed to a Flawed Automated Endoscope Washer-Disinfector in a Digestive Diseases Unit

The possible transmission of pathogens to 236 persons exposed to an endoscope processed in a flawed automated endoscope washer-disinfector in a gastrointestinal endoscopy unit was investigated. During 6 months, 197 patients (83.5%) were followed up, and no cases of acute human immunodeficiency virus, hepatitis C virus, or hepatitis B virus infection were observed. This event created the conditions for improvements in safety procedures.

Bacteria-free endoscopy rinse water – a realistic aim?

A number of outbreaks and pseudo-outbreaks have been associated with contaminated rinse water in endoscope washer-disinfectors. Health Technical Memorandum 2030 specifies that final rinse water should be 'bacteria-free'. In this study, results of rinse-water testing from 20 endoscopy units were reviewed over a 4-month period. Over 60% of samples were of an unsatisfactory quality (i.e. not bacteria-free) and none of the endoscopy units consistently achieved sterile water throughout the study period. Poor microbiology results caused anxiety to endoscopy staff and infection control teams who had to decide whether or not to take washer-disinfectors out of use, possibly resulting in delays to medical procedures. There was no common policy on how to react to poor results, with staff at each unit developing their own action levels. Here, it is suggested that future guidelines would be of more practical use if they specified a series of action levels of increasing severity based on the bacterial count in a water sample.

Gastroscope processing in washer–disinfectors at three different temperatures

Endoscopes are processed chemo-thermally at approximately 56 °C in washer–disinfectors in Germany. In this study we investigated the processing of gastroscopes by an endoscope washer–disinfector at different temperatures. A total of 87 gastroscopes were tested hygienically and microbiologically before manual cleaning (after patient use), as well as after manual cleaning and after endoscope washer–disinfector processing at running temperatures of 43, 51 and 56 °C. In all tests the suction/biopsy channels of the gastroscopes were flushed with 50 mL sterile solution throughout their full length, from the proximal to the distal ends. The rinse solutions were plated on to various culture media. Also, in order to detect low bacterial counts, 3×10 mL rinse solution was membrane filtrated. The German guideline level for total bacterial counts, applicable since 2002, was exceeded at all temperatures tested (159 cfu/mL at 43 °C, <60 cfu/mL at 51 °C, and 8 cfu/mL at 56 °C). A temperature increase from 43 to 51 °C resulted in a highly significant reduction of the residual contamination by aerobic bacteria ( P<0.001, Mann–Whitney U Test), Gram-negative bacilli ( P<0.001), and pseudomonads ( P=0.002). A further temperature increase from 51 to 56 °C resulted in a further highly significant drop in residual contamination by aerobic bacteria ( P=0.021) and pseudomonads ( P=0.036). The aim of the user—minimizing material damage to endoscopes or prolonging their product life—cannot be achieved through lowering the processing temperature without putting patients at risk. In order to ensure adequate processing, endoscope washer–disinfectors should meet the requirements of current draft standards.

Determination of glutaraldehyde residues on flexible endoscopes after chemothermal treatment in an endoscope washer-disinfector.

Although there are several cases of glutaraldehyde-induced colitis following colonoscopy there is only one study on residues after disinfecting. Our report describes the determination of water-soluble glutaraldehyde residues after processing endoscopes with a glutaraldehyde-containing disinfectant. A gastroscope and a colonoscope were processed in a washer-disinfector and then immersed in 201 of NaCl solution. Glutaraldehyde was determined by high performance liquid chromatography in 84 samples. Samples were taken after immersing the endoscopes for 5 h and 24 h with and without rinsing the channels. After 5 h and with the channels having been rinsed, the median for colonoscopes was only 0.409 mg/l. The highest level of glutaraldehyde was 0.846 mg/l. After endoscopes have been processed in the washer-disinfector there is no risk of a glutaraldehyde-induced colitis, proctitis or diarrhoea.

An outbreak of multidrug-resistant Pseudomonas aeruginosa infection associated with contamination of bronchoscopes and an endoscope washer-disinfector

Over a two-month period, two distinct types of Pseudomonas aeruginosa resistant to ceftazidime and azlocillin were isolated from bronchial specimens of ITU patients who had been previously bronchoscoped. The source of the outbreak was probably a faulty contaminated bronchoscope washer-disinfector which had been purchased a year earlier but not properly maintained. This paper describes the outbreak, the identification and elimination of the source, and the steps taken to prevent recurrence. Several automated, closed washer-disinfectors had been bought by the hospital in response to health and safety concerns about glutaraldehyde disinfection toxicity, but the operation and maintenance of these machines had not been supervised. Several other washer-disinfectors were also found to be faulty. The potential hazards of automated endoscope washer-disinfectors and the importance of controlled professional maintenance, servicing and training is discussed.

Reduced glutaraldehyde susceptibility in Mycobacterium chelonae associated with altered cell wall polysaccharides.

Glutaraldehyde-resistant Mycobacterium chelonae have been isolated from endoscope washer disinfectors and endoscope rinse water. The mechanism of glutaraldehyde resistance is not well understood. Two spontaneous, glutaraldehyde-resistant mutants of the sensitive type strain, NCTC 946, were investigated. The colony morphology of the two mutants differed from that of the the type strain: colonies of the former were dry and waxy whereas those of the latter were smooth and shiny. Increased resistance to glutaraldehyde of the mutants was matched by small increases in the MICs of rifampicin and ethambutol but not isoniazid. Both mutants showed increased surface hydrophobicity. No changes were identified in the extractable fatty acids or the mycolic acid components of the cell wall but a reduction in each of the resistant strains in the arabinogalactan/arabinomannan portion of the cell wall was detected.

Mycobactericidal activity of selected disinfectants using a quantitative suspension test

In this study, a quantitative suspension test carried out under both clean and dirty conditions was used to assess the activity of various instrument and environmental disinfectants against the type strain NCTC 946 and an endoscope washer disinfector isolate of Mycobacterium chelonae, Mycobacterium fortuitum NCTC 10394, Mycobacterium tuberculosis H37 Rv NCTC 7416 and a clinical isolate of Mycobacterium avium-intracellulare (MAI). The disinfectants tested were; a chlorine releasing agent, sodium dichloroisocyanurate (NaDCC) at 1000 ppm and 10 000 ppm av Cl; chlorine dioxide at 1100 ppm av ClO 2 (Tristel, Medichem International Limited); 70% industrial methylated spirits (IMS); 2% alkaline glutaraldehyde (Asep, Galan); 10% succinedialdehyde and formaldehyde mixture (Gigasept, Schulke & Mayr); 0·35% peracetic acid (NuCidex, Johnson & Johnson); and a peroxygen compound at 1% and 3% (Virkon, Antec International). Results showed that the clinical isolate of MAI was much more resistant than M. tuberculosis to all the disinfectants, while the type strains of M. chelonae and M. fortuitum were far more sensitive. The washer disinfector isolate of M. chelonae was extremely resistant to 2% alkaline activated glutaraldehyde and appeared to be slightly more resistant than the type strain to Nu-Cidex®, Gigasept®, Virkon® and the lower concentration of NaDCC. This study has shown peracetic acid (Nu-Cidex), chlorine dioxide (Tristel®), alcohol (IMS) and high concentrations of a chlorine releasing agent (NaDCC) are rapidly mycobactericidal. Glutaraldehyde, although effective, is a slow mycobactericide. Gigasept and Virkon are poor mycobactericidal agents and are not therefore recommended for instruments or spillage if mycobacteria are likely to be present.

Endoscope decontamination: automated vs. manual

Automated endoscope washer disinfectors are widely used for the decontamination of flexible endoscopes. They are more effective than manual techniques and reduce the likelihood of skin contact with irritant disinfectants. Suitable machines are those which effectively clean, disinfect and rinse all channels and external surfaces without damaging the instrument. If glutaraldehyde is used, fumes should be removed or contained to protect endoscopy and processing staff. Machines should also be equipped with a self-disinfect facility and the rinse water should be of a suitable micro-biological quality for the instruments processed, i.e. bacteria-free (sterile or filtered) water should be used for bronchoscopes and all invasive endoscopes. The choice of machine and cycle will depend on the following: whether a mobile or fixed unit is required; the type of disinfectant used; instrument throughput; and whether or not it is necessary to process more than one endoscope at a time. Purchasers are advised to request independent test reports which substantiate manufacturers' claims.