Washer Disinfector Research Articles

Measuring of ATP bioluminescence as a means of assessing washer disinfector performance and potentially as a means of validating the decontamination process

This paper reports on the results of using a commercially available adenosine tri-phosphate bioluminescence (ATP) hand-held device for assessing the level of contamination on surgical instruments throughout the decontamination process. The report demonstrates that this technique may be a reliable point-of-use method for quantitatively assessing washer disinfector function and possibly a means of performing a washer disinfector validation process.

Quantitative measurement of the efficacy of protein removal by cleaning formulations; comparative evaluation of prion-directed cleaning chemistries

The stability of the infectious agent causing variant Creutzfeldt-Jakob disease (vCJD) has highlighted the importance of cleaning surgical instruments for controlling potential spread of iatrogenic CJD. In this study, thermostable adenylate kinases (tAKs) in test soil were coated on to stainless steel and these surrogate agents used to evaluate the efficacy of a range of cleaning chemistries in a bench-top washer disinfector (btWD), or as a pre-soak either with or without subsequent treatment by btWD. Two tAKs were tested initially for ease of removal, the most persistent being Sulfolobus acidocaldarius-derived tAK which was used for evaluating the cleaning chemistries. Conventional chemistries were generally more effective when used in a btWD than as pre-soaks. Cleaning efficacy improved when pre-soaks were followed by treatment with intermediate performing enzymes, demonstrating greater than additive effect on residual tAK activity. Three of the four prion-directed chemistries reduced residual tAK activity to below the limit of quantification (LoQ) by more than 4.8 log(10); <175pg tAK remaining as a pre-soak alone. A conventional alkaline cleaning product also reduced residual tAK activity to below the LoQ but only when used in a btWD. tAK soil dried on to the device was removed less efficiently than tAK soil still moist on the device, with a 320-fold and 28-fold increase in residual tAK activity for pre-soak and btWD, respectively. The study demonstrated the potential for a tAK indicator to describe the effectiveness of protein removal using different chemistries or treatment processes.

Thermostable adenylate kinase technology: a new process indicator and its use as a validation tool for the reprocessing of surgical instruments

Adenylate kinase (tAK), a thermostable enzyme, was assessed as a possible means of providing a quantitative measure of cleaning efficacy suitable for validating the performance of an automated washer disinfector (AWD) during routine use. Two indicator formulations were developed using either a commercially available washer disinfector soil or a protein-based soil. Each indicator consisted of 100 microg (in test soil) of tAK dried on to a steel or plastic surface. These indicators were placed in each basket of a washer disinfector and processed alongside soiled surgical instruments during a standard day's operation. After processing, remaining tAK activity was detected using a rapid enzyme assay (2 min detection time) in a handheld hygiene monitor. The amount of tAK remaining on each indictor after a full AWD cycle was found to range from 0.1 to 0.4 ng, which represented a mean log(10) removal of 5.8+/-0.3. There was no statistical difference in the residual tAK activity between individual runs or the position of the indicator in the machine. The tAK indicator was also used to analyse the protein removal within each component of the wash cycle. These results demonstrated that all phases of the wash process contributed to the removal of the protein load, with the main wash alone being responsible for 3.6-4.0 log(10) reductions in protein activity. We propose that a quantitative cleaning index using such rapid readout indicator devices would provide a valuable addition to the methodologies for validating cleaning processes.

Cleaning endodontic files in a washer disinfector

The aim of this study was to compare the cleanliness of endodontic files that had been cleaned in a washer disinfector according to the file holding mechanism within the machine. Selected canals of extracted teeth were filed with new, unused files. One set of files (size 15 to 40) was used for each canal. A total of 192 files were used for cleaning and shaping. The files were divided into three groups. The first group was a control group containing 30 files, which were not cleaned in the washer disinfector. The second and the third groups were the experimental groups with 81 files in each group. These files were cleaned in the washer disinfector using different holding mechanisms (file holder or cleaning basket) for each group. The files were examined for visible debris under a light microscope at x45 magnification. None of the 162 cleaned files were totally free of organic debris. Comparison of the debris scores in the two experimental groups showed that the files in the cleaning basket group were significantly cleaner than those in the file holder group. The files in both test groups were significantly cleaner than those in the control group. Endodontic files cannot be totally cleaned using a washer disinfector alone. The instrument holding mechanism within the machine has a significant effect on the cleanliness of the files after one intensive cleaning cycle.

Summary of: Cleaning endodontic files in a washer disinfector

Aims The aim of this study was to compare the cleanliness of endodontic files that had been cleaned in a washer disinfector according to the file holding mechanism within the machine. Methodology Selected canals of extracted teeth were filed with new, unused files. One set of files (size 15 to 40) was used for each canal. A total of 192 files were used for cleaning and shaping. The files were divided into three groups. The first group was a control group containing 30 files, which were not cleaned in the washer disinfector. The second and the third groups were the experimental groups with 81 files in each group. These files were cleaned in the washer disinfector using different holding mechanisms (file holder or cleaning basket) for each group. The files were examined for visible debris under a light microscope at x45 magnification. Results None of the 162 cleaned files were totally free of organic debris. Comparison of the debris scores in the two experimental groups showed that the files in the cleaning basket group were significantly cleaner than those in the file holder group. The files in both test groups were significantly cleaner than those in the control group. Conclusions Endodontic files cannot be totally cleaned using a washer disinfector alone. The instrument holding mechanism within the machine has a significant effect on the cleanliness of the files after one intensive cleaning cycle.

Comparison of an ultrasonic cleaner and a washer disinfector in the cleaning of endodontic files

The aim of this study was to compare the amount of residual organic debris on endodontic instruments that had been cleaned in either an ultrasonic bath or a washer disinfector prior to sterilisation. A total of 90 endodontic files of varying sizes were used to clean and shape root canals in extracted teeth and were then placed in endodontic file holders. Test group 1 (36 files) were ultrasonically cleaned for 10 min and test group 2 (36 files) were cleaned in a washer disinfector. A control group (18 files) were not cleaned at all. Following sterilisation, all the files were visually inspected under a light microscope and scored using an established scale. The results showed that both test groups had significantly less residual debris than the control group. Comparing the test groups, the files that had been cleaned ultrasonically had significantly less debris than those cleaned in the washer disinfector. The design of the instrument holder may have been a factor in this result. More research is needed into the use of washer disinfectors in the cleaning of small dental instruments that have a complex surface structure.

Intervention for proper use and unification of disinfectants The use of washer disinfector

Intervention for proper use and unification of disinfectants The use of washer disinfector

Comparison of economic and environmental impacts between disposable and reusable instruments used for laparoscopic cholecystectomy

The economic and environmental effects were compared between disposable and reusable instruments used for laparoscopic cholecystectomy. Special consideration was given to the processing of reusable instruments in the Miele G 7736 CD MCU washer disinfector and the resultant cost of sterilization. The instruments frequently used in their disposable form were identified with the help of surgeons. Thus, of all the instruments used for laparoscopic cholecystectomy, the disposable and reusable versions of trocars, scissors, and Veress cannula were compared. For the case examined in this study, the performance of laparoscopic cholecystectomy with disposable instruments was 19 times more expensive that for reusable instruments. The higher cost of using disposable instruments is primarily attributable to the purchase price of the instruments. The processing of reusable instruments has little significance in terms of cost, whereas the cost for disposing of disposable instruments is the least significant factor. The number of laparoscopic cholecystectomies performed per year does not substantially influence cost. In the authors' opinion, assessment of the environmental consequences shows that reusable instruments are environmentally advantageous. Considering the upward pressure of costs in hospitals, disposable instruments should be used for laparoscopic cholecystectomy only if they offer clear advantages over reusable instruments.

Reprocessing endoscopes: national recommendations with a special emphasis on cleaning—the German perspective

Transmission of pathogens through endoscopes or endoscopic procedures has been documented frequently, although reliable data on the incidence of endoscope-associated infections do not exist. In order to control such infections as well as to ensure adequate quality management in endoscopy, the German Robert Koch Institute has produced recommendations for hygienic processing of flexible endoscopes and accessory devices. Reprocessing using a washer disinfector is explicitly preferred to manual procedures. Control measures are focused on microbiological sampling and limiting values have been defined for rinsing fluids taken from the channels of the scopes. Although the guideline leaves a number of questions open, e.g. test methods to control the efficacy of the cleaning process. It helps to establish quality management in the field of endoscopy and to improve the level of safety both for patients and staff.

Efficacy of 10 different cleaning processes in a washer–disinfector for flexible endoscopes

Successful cleaning of medical devices, such as flexible endocopes, has been recognized to be of major importance for effective processing. Washer–disinfectors (WD) are considered to be an important step in this direction. The cleaning process in WD, however, has only been partially assessed regarding its effectiveness, and therefore to study this in more detail, tests were carried out, according prEN ISO 15883, using transparent teflon tubes as test pieces (length 2 m). For each experiment three test pieces were contaminated with the ‘German test soil’ containing Enterococcus faecium in blood, two for the test and one as a control (no automatic cleaning). Automatic cleaning was performed with a Wassenburg WD 440. Ten cleaning agents were used. In addition the process was carried out with water alone. After automated cleaning, test pieces were assessed visually (four categories, range: very poor to excellent visible cleanliness) and microbiologically [log 10 reduction factor (RF)]. Each experiment was repeated three times. Using the WD water gave excellent visible cleanliness with a mean RF of 1.1±0.6. The same excellent visible cleanliness was obtained with seven cleaning processes: deconex ® 23 Neutrazym, Helimatic Cleaner enzymatic, Korsolex ®-Endo-Cleaner, Labomat E, neodisher ® mediclean, Thermosept ® ER, and Thermoton NR. Worse visible cleanliness was found with three cleaning processes: Olympus ETD Cleaner and neodisher FE led to adequate visible cleanliness, and the cleaning process with neodisher medizym led to poor visible cleanliness. Six cleaning processes reduced the test organism by RF≥3, i.e. the reduction was significantly higher than after cleaning with water alone. No significant difference between use of water alone and the cleaning process was found with three cleaning processes: Olympus ETD Cleaner, neodisher mediclean, and Thermosept ER (range RF: 0.8–1.8; P>0.05). The cleaning process with neodisher medizym yielded a significantly lower mean RF ( P=0.039) in comparison with water treatment alone. Both visible cleanliness and mean RF, varied indicating that the choice of cleaning process had a major impact on the overall result.

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.

Cleaning efficacy of nine different cleaners in a washer–disinfector designed for flexible endoscopes

Studies on processing endoscopes usually involve the combined cleaning and disinfecting activity. We compared nine cleaning agents designed for automatic processing for cleaning efficacy alone using soft and hard water as controls in 12 different processes in a washer–disinfector. Experiments were performed according to the German Endoscopy Working Group recommendations using transparent Teflon tubes (internal diameter 2 mm, length 2 m) as test pieces. For each test three pieces contaminated with a blood/test soil containing Enterococcus faecium were used; two for the test and one as a control; each test was repeated three times. Tests were run according to the manufacturer's instructions. Test pieces were assessed visually and microbiologically [log 10 reduction factors (RF) vs. untreated controls]. Soft water alone gave poor visible cleanliness and an RF of 0.3 ( SD 0.2), while hard water produced adequate visible cleanliness and an RF of 1.2 ( SD 1.0). Five processes gave better visible cleanliness than soft water, but only three were better than hard water. Six processes were worse than soft water and five worse than hard water. Nine processes gave a better microbiological reduction factor than soft water, but the difference was only statistically significant in three. Only one process yielded a significantly higher RF than hard water; three were significantly worse. None of the cleaning processes reached the RF of 4 specified in the US regulations. This study confirms the variability of cleaning processes to dissolve blood residues and reduce the bioburden. We do not recommend abandoning cleaning agents, but suggest that further research is needed to clarify the relationships between washer–disinfectors, cleaning agents, and cleaning performance.

Comparison of the mycobactericidal activity of ortho- phthalaldehyde, glutaraldehyde and other dialdehydes by a quantitative suspension test

The mycobactericidal activity of various dialdehydes has been assessed by a quantitative suspension test in both 'clean' and 'dirty' conditions. Test organisms consisted of glutaraldehyde (GTA)-sensitive strains of Mycobacterium chelonae NCTC 946, M. abscessus NCTC 10882, two GTA-resistant M. chelonae strains and M. terrae NCTC 10856 (a proposed M. tuberculosis surrogate). The aldehydes tested were a new high-level disinfectant, ortho-phthalaldehyde (OPA) at 0.5% (v/v) unadjusted pH 6.5 and pH 8, GTA at 0.5% (v/v) pH 8, glyoxal at 0.5% (v/v) pH 8 and 10% (v/v) unadjusted pH 2.8, malonaldehyde sodium salt (NaMDA) at 0.5% (w/v) pH 8 and 10% (w/v) unadjusted pH 7.5 and succinaldehyde at 0.5% (v/v) pH 8. Results showed that 0.5% acidic and alkaline OPA were rapidly mycobactericidal, under both 'clean' and 'dirty' conditions, and more importantly were active against GTA-resistant strains. The washer disinfector isolates of M. chelonae were, as expected, extremely resistant to 0.5% GTA which was slowly mycobactericidal against the other strains. Glyoxal, NaMDA and succinaldehyde were ineffective against all the strains investigated. However, a high concentration of glyoxal exhibited a slow mycobactericidal activity except with M. terrae NCTC 10856, but this was not observed with NaMDA. This evaluation, using a quantitative suspension test based on a European standard, supported the claim that OPA is an effective choice as a high-level disinfectant for medical devices.

Choosing instrument disinfectants and processors

The thorough cleaning and high-level disinfection or sterilisation of heat sensitive instruments and equipment, preferably using a validated washer disinfector and an effective, non-damaging disinfectant, will minimise the risk of infection, prolong the life of the device and protect the quality of diagnostic samples. No disinfectant or washer disinfector meets all the preferred selection criteria at present, but a careful appraisal of the options, using the criteria outlined, will enable you to choose a processor and disinfectant that more nearly meet your requirements.

Évaluation de sept laveurs-désinfecteurs d'endoscopes : activité bactéricide des désinfectants, efficacité antibactérienne des couples laveur-désinfecteur/produits

The authors studied seven automatic washer disinfectors for flexible endoscopes with two methods. The first method, a microdilution method, studied the bactericidal activity of the seven disinfectants against 21 strains: four reference strains, 14 hospital strains reported in the literature as nosocomial strains responsible for infections transmitted by flexible endoscopes and three vancomycin-resistant Enterococci. The ability of the seven automatic washer disinfectors to decontaminate flexible endoscopes following inoculation with four reference strains was studied with the second method. There were three kinds of results: the results of three automatic washer disinfectors in conformity with both methods; the results of three automatic washer disinfectors conformity with 1 method only; the results of one automatic washer disinfector without conformity with any methods. Both methods should be used for evaluation of automatic washer disinfector. Then, these results emphasize the necessity to modify the use of disinfectants and/or the systems of some automatic washer disinfectors.

Evaluation of the cleaning and disinfectionefficacy of the DEKO-190; a ward-basedautomated washer/disinfector

The DEKO-190 Washer–Disinfector combines both automatic washing and thermal disinfection functions and is designed for the decontamination of ward utensils (such as bedpans and urine bottles) and instruments used in minor surgery prior to sterilization. We undertook a microbiological evaluation of the disinfection efficacy of the machine, using its short wash plus disinfection programme and sealed suspensions of test organisms placed at various points within the instrument. Suspensions ofEnterococcus faecalis and Poliovirus were totally inactivated, the counts of aerobic organisms within a stool specimen being reduced by a factor of 104whilst spores of Clostridium perfringens were unaffected. The cleaning efficacy of the DEKO-190 was also evaluated under clinical conditions by visual inspection and was found to be satisfactory. Ward-based combined washer–disinfection machines, such as the DEKO-190, have the potential to improve the efficacy of cleaning protocols within healthcare institutions.

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.

Glutaraldehyde-resistant Mycobacterium chelonae from endoscope washer disinfectors.

Glutaraldehyde is used to disinfect flexible and other heat-sensitive endoscopes often with the aid of automated systems. Mycobacterium chelonae is being isolated with increasing frequency from these washer disinfectors and processed endoscopes. This has, on occasions, led to misdiagnosis and iatrogenic infections. Recent reports suggest that disinfecting machines, on a sessional or regular basis, with 2% glutaraldehyde may have selected and therefore encouraged the growth of strains of Myco. chelonae, possibly in biofilm, with decreasing susceptibility to glutaraldehyde. In view of this, the resistance of three strains of Myco. chelonae var. chelonae (the type strain NCTC 946 and two machine isolates) was tested against 2% glutaraldehyde and a wide range of alternative disinfectants. Disinfectants tested were a chlorine releasing agent, sodium dichloroisocyanurate at 1000 ppm and 10,000 ppm av Cl, 0.35% peracetic acid (NuCidex, Johnson & Johnson), 70% industrial methylated spirit (IMS), 1% peroxygen compound ('Virkon', Antec International) and 10% succine dialdehyde ('Gigasept', Sanofi Winthrop). Suspension and carrier tests were carried out in the presence and absence of an organic load. Results showed the type strain, which had not been exposed to the selective pressure of disinfectant usage, to be very sensitive to most disinfectants with the exception of 1% Virkon. The washer disinfector isolates, on the other hand, were extremely resistant to 2% glutaraldehyde and showed greater resistance to 1% Virkon and 1000 ppm NaDCC. Purchasing machines in which the entire fluid pathways, including those for delivering rinse water, are disinfected with an appropriate agent during each cycle are preferred. If this is not possible then sessional cleaning and disinfection at the start of each day and regular maintenance should prevent biofilm formation and contamination with disinfectant-resistant strains of mycobacteria. In addition to machine disinfection, the use of sterile or bacteria-free (filtered < 0.45 microm) water is essential for bronchoscopes and all invasive endoscopes. If there is doubt that the effectiveness of the machine disinfection procedure or water quality, the channels and surfaces of endoscopes may be rinsed with 70% IMS after automated processing.

Washer Disinfector(Special Issue : Prevention of Infection Caused by Medical Instruments and Devices (1))

Washer Disinfector(Special Issue : Prevention of Infection Caused by Medical Instruments and Devices (1))