A test for cleaning and disinfection processes in a washer-disinfector

Comparison of washer-disinfector cleaning indicators: impact of temperature and cleaning cycle parameters

BACKGROUND

Because automated instrument washer-disinfectors (WD) are widely used in health care to reprocess a variety of medical instruments, we developed a study to compare 3 cleaning indicators to determine whether they detected suboptimal temperature, time, enzymatic detergent, and fluid action in a washer-disinfector.

METHODS

The Miele WD was used for this comparison. One optimal cycle and 14 cycles with suboptimal enzymatic detergent, cleaning time, temperature, or inactive spray arms were evaluated. The cleaning indicators evaluated included the following: Pinnacle Monitor for Automated Enzymatic Cleaning Process (PNCL), Wash-Checks (WC), and TOSI. The scoring system for all 3 indicators was harmonized to a common scale. Soiled tweezers were included in each cycle evaluated.

RESULTS

The PNCL, TOSI, and WC cleaning indicators showed significantly more failures at 40°C compared with 60°C (100% vs 0% for PNCL, 17% vs 0% for TOSI, and 60% vs 22% for WC, respectively). There were significantly more failures at suboptimal temperatures with a 2- versus 4-minute cycle (100% vs 0% for PNCL, 17% vs 0% for TOSI, and 17% vs 0% for WC, respectively, for 40°C cycles). Despite suboptimal cleaning cycles, all soiled tweezers looked clean.

CONCLUSION

All 3 cleaning indicators responded to suboptimal WD conditions; however, the PNCL was the most affected by alterations in the cycle conditions evaluated. In simulated use testing, cleaning indicators provided a more sensitive audit tool compared with visual inspection of soiled instruments after automated cleaning.

Acquisition of proteinaceous contamination through the handling of surgical instruments by hospital staff in sterile service departments

Using Episcopic Differential Interference Contrast (EDIC) microscopy, this study has investigated the potential reapplication of prote ina ceouscontami napotential reapplication of proteinaceous contamination onto surgical instruments following a washer-disinfector cycle through the handling of staff within the clean room. The deposition of 0.51 ng/mm2 of protein onto surgical grade stainless steel by one finger print alone has been demonstrated. Moreover, using a previously described contamination index, a 5 to 10-fold increase in protein present on surgical instruments was noted following handling by clean-room staff under current departmental practices, relative to instruments handled by staff wearing gloves. While unlikely to pose a direct risk to patient health, subsequent sterilisation will fix protein to an instrument surface thereby decreasing the effectiveness of further decontamination cycles. Current guidelines make no recommendations surrounding the use of gloves by staff working within the clean room. However it is clear that this matter must be reviewed to limit the unnecessary transference of protein to surgical instruments.

Simulated-use testing of bedpan and urinal washer disinfectors: evaluation of Clostridium difficile spore survival and cleaning efficacy

BACKGROUND

Reusable bedpans and urinals are frequently cleaned and decontaminated using washer-disinfectors (WDs) that may be located in the central processing department (CPD) or on the ward. The objective of this study was to determine how efficiently the WDs provided cleaning and to evaluate the ability of such WDs to kill Clostridium difficile spores.

METHODS

The cleaning efficacy of 2 bedpan/urinal WDs (1 in the ward [ward-WD] and 1 in the CPD [CPD-WD]) were evaluated using simulated-use testing that included an ultraviolet-visible marker (UVM) that is readily removed when exposed to liquid. In addition, a proprietary test object surgical instrument (TOSI) device was used to assess the efficacy of the WDs. Artificial test soil (ATS) and C. difficile spore removal and killing also were evaluated. The removal of approximately 10(6) C. difficile spores and subsequent killing of these spores was assessed using autoclaved stool and/or urine as the soil challenge.

RESULTS

Reusable stainless steel bedpans, plastic bedpans, and plastic urinals were assessed. Triplicate testing done on 3 separate days using TOSI devices, UVM, ATS, and stool and urine soils indicated that the ward-WD did not demonstrate adequate cleaning. It was determined that installation errors accounted for the inadequate cleaning. But the ward-WD did not adequately inactivate C. difficile spores even when the installation problems were corrected and the manufacturer-adjusted maximal thermal conditions were used. The CPD-WD was able not only to adequately clean the test devices of organic soil, but also to completely inactivate the 6 logs of C. difficile spores placed in sealed ampules inside the WD.

CONCLUSION

The results of this study indicate that user testing of the efficacy of WDs is critical to ensure appropriate functionality. The currently accepted thermal decontamination parameters for all bedpan WDs (ie, 80 degrees C for 1 minute) are not adequate to eliminate C. difficile spores from bedpans.

Automated washing with the Reliance Endoscope Processing System and its equivalence to optimal manual cleaning

BACKGROUND

Manual cleaning of flexible endoscopes is prone to error. To date, attempts to automate this process have been unsuccessful. The aim of this project was to compare the efficacy of the washing phase in the new Reliance EPS (STERIS Corp, Mentor, OH) with that of optimal manual cleaning.

METHODS

Using simulated-use testing, all channels in 3 different flexible endoscopes, including a bronchoscope (Pentax, Pentax Medical Company, Miami, FL), a side-viewing duodenoscope (Olympus, Olympus Corporation), and a colonoscope (Fujinon, Fujinon Corporation, Wayne, NJ) were evaluated. All of the channels in the flexible endoscope were soiled with artificial test soil (ATS) (test soil that mimics the worst case levels of hemoglobin, protein, carbohydrate, and endotoxin from patient-used flexible endoscopes) containing 10(8) cfu/mL of Enterococcus faecalis and Pseudomonas aeruginosa The soiled scopes were allowed to dry for 1 hour prior to processing. Hemoglobin, protein, and viable organism counts for the flexible endoscopes were determined before and after cleaning.

RESULTS

Both the Reliance EPS washing phase and optimal manual cleaning achieved >90% reduction of hemoglobin and protein, resulting in <6.4 microg/cm2 after the cleaning cycle. The reduction factor for viable organisms was not significantly different between the 2 methods, which ranged from 2.06 to 6.21 for manual cleaning and from 2.1 to 5.93 for the Reliance EPS washing phase. The mean reduction factor (all tests) was 4.32 +/- 1.03 for manual cleaning compared with 4.24 +/- 1.11 for Reliance EPS washing phase.

CONCLUSION

The efficacy of the Reliance EPS washing phase for flexible endoscopes was equivalent to optimal manual cleaning for all the makes and models of flexible endoscopes tested.

Surface decontamination of surgical instruments: an ongoing dilemma

The issues of cross-infection and the survival of variant Creutzfeldt Jakob disease (vCJD) on surgical instruments have highlighted the importance of cleanliness of multiple-use surgical instruments. The aim of this study was to assess the levels of total protein contamination on a wide range of surgical instruments as an indication of the effectiveness of routine cleaning and disinfection in hospitals. Anonymized trays of wrapped and autoclaved instruments were supplied to two laboratories for analysis at the stage where they would normally be returned to operating theatres. Instruments were assessed for residual protein and total organic matter. Laboratory A showed that 17% (35/206) of instruments were above a threshold that equated to 200 microg. The worst examples, a McIvor gag, a Draffin rod (child) and a Yankaur sucker, had 1.028, 1.286 and 2.228 mg of extractable protein, respectively. The median (25th, 75th percentiles) amount of protein from instruments from different hospitals assessed in Laboratory B ranged from 8 (3, 30)mug (Hospital C) to 91 (35, 213) mug (Hospital D) (P=0.044). The residual matter washed from instruments varied from 0.62 (0.32, 0.81) mg (Hospital E) to 3.5 (3.5, 4.0) mg (Hospital A) (P=0.0001). In one case, 45 mg of residual organic matter was washed from an instrument (split stem). In conclusion, this study demonstrated that a proportion of instruments at the point of use show levels of protein that could pose a direct cross-infection risk via prion agents and other organic contamination that may reduce the effectiveness of cleaning/disinfection strategies targeted against either prions or traditional infectious agents.

Alcoholic fixation of blood to surgical instruments—a possible factor in the surgical transmission of CJD?

While developing a new protein removal test for the quality control of surgical instrument cleaning, it was noted that alcohol firmly binds blood to stainless steel. Creutzfeldt-Jacob disease is one of the transmissible spongiform encephalopathies (TSE) that has been transmitted between humans and chimpanzees by electroencephalogram electrodes, previously 'sterilized' using ethanol and formaldehyde. Although ethanol has a bactericidal action, it also binds protein to metal. Prion proteins found in TSE are thought to be the causal agents of spongiform disease and it is likely that these proteins are also bound to the stainless steel of surgical instruments by alcohols. Where spongiform disease is a possibility, alcohol, and probably formaldehyde, should not be used to decontaminate neurosurgical instruments.