Evaluation of an overnight non-culture test for detection of viable Gram-negative bacteria in endoscope channels.

Background and study aims Prevention of infection transmission from contaminated endoscopes would benefit from a rapid test that could detect low levels of viable bacteria after high level disinfection. The aim of this study was to evaluate the rapid NOW! (RN) test's ability to detect endoscope contamination. Materials and methods The RN test kit and the accompanying fluorometer were evaluated. The manufacturer states that a fluorometer signal > 300 units is indicative of viable Gram-negative bacteria. Suspension testing of varying concentrations of Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis were used to determine the RN test limit of detection. Simulated-use testing was done using a duodenoscope inoculated with 10 % blood containing approximately 35 CFU E. coli per channel. Samples were extracted from the duodenoscope instrument channel and tested using the manufacturer's instructions. Results The RN test could consistently detect 10 CFU of E. coli and P. aeruginosa (fluorescent signal of 9,000 to 11,000 units) but not E. faecalis. Sensitivity and specificity for Gram-negative bacteria were 93 % and 90 %, respectively, using all of the suspensions in the study. Extraction of E. coli from an inoculated duodenoscope instrument channel repeatedly provided a positive signal (i. e. > 2,000 units). Conclusions The RN test can reliably detect low levels of Gram-negative bacteria in suspension as well as from samples extracted from endoscope channels. These preliminary findings are encouraging but further assessment of extraction efficacy, impact of organic residuals and clinical workflow are still needed.

Impact of cleaning monitoring combined with channel purge storage on elimination of Escherichia coli and environmental bacteria from duodenoscopes.

BACKGROUND AND AIMS: We aimed to determine whether monitoring of duodenoscope cleaning by rapid adenosine triphosphate (ATP) combined with channel-purge storage could eliminate high-concern microorganisms. METHODS: In a simulated-use study, suction channels, as well as lever recesses, from 2 duodenoscopes models and the unsealed elevator guidewire (EGW) channel from 1 of these 2 duodenoscopes (the other model has a sealed EGW) were perfused with ATS2015 containing approximately 8 Log10 colony-forming units (CFU)/mL of both Enterococcus faecalis and Escherichia coli. Pump-assisted cleaning was monitored by rapid ATP testing. Duodenoscopes exceeding 200 relative light units (RLUs) were recleaned. Clean duodenoscopes were processed through an automated endoscope reprocessor and then stored in a channel-purge storage cabinet for 1 to 3 days. Cultures of EGW channel and instrument channel combined with the lever recess (IC-LR) were taken after storage. The impacts of extended cleaning and alcohol flush were evaluated. RESULTS: E coli was reliably eliminated in IC-LR and EGW channels of 119 duodenoscope tests (59 with sealed EGW and 60 with nonsealed EGW). However, actionable levels of E faecalis and environmental bacteria persisted. Neither alcohol flush nor extended cleaning resulted in a reduction of actionable levels for these organisms. Identification of isolates indicated that residual organisms in duodenoscope channels were hardy Gram-positive bacteria (often spore formers) that likely originated from environmental sources. CONCLUSIONS: These data indicate that high-concern Gram-negative bacteria but not E faecalis or environmental bacteria can be reliably eliminated by use of the manufacturer's instructions for reprocessing with ATP monitoring of cleaning and channel-purge storage conditions.

Improper positioning of the elevator lever of duodenoscopes may lead to sequestered bacteria that survive disinfection by automated endoscope reprocessors.

BACKGROUND: Some outbreaks associated with contaminated duodenoscopes have been attributed to biofilm formation. The objective of this study was to determine whether bacteria within an organic matrix could survive if the elevator lever was improperly positioned in the automated endoscope reprocessor (AER) after 1 round of reprocessing. METHODS: Duodenoscope lever cavities with an open or sealed elevator wire channel were inoculated with 6-7 Log10 of both Escherichia coli and Enterococcus faecalis in ATS2015 (Healthmark Industries, Fraser, MI) and dried for 2 hours. The duodenoscopes with the lever in the horizontal position were processed through 2 makes of AERs. The cavity was sampled using a flush-brush-flush method to determine the quantity of surviving bacteria. RESULTS: E faecalis (range, 21-6 Log10 CFU) and E coli (range, 0-3 Log10 CFU) survived disinfection of sealed or unsealed elevator wire channel duodenoscopes in 2 different AERs with and without cleaning cycles. CONCLUSION: If bacteria in organic residue are under the improperly positioned lever, then just 1 round of use is sufficient for bacteria to survive both liquid chemical sterilization and liquid chemical HLD regardless of whether or not the AER had a cleaning cycle.

Sterile Reverse Osmosis Water Combined with Friction Are Optimal for Channel and Lever Cavity Sample Collection of Flexible Duodenoscopes.

INTRODUCTION: Simulated-use buildup biofilm (BBF) model was used to assess various extraction fluids and friction methods to determine the optimal sample collection method for polytetrafluorethylene channels. In addition, simulated-use testing was performed for the channel and lever cavity of duodenoscopes. MATERIALS AND METHODS: BBF was formed in polytetrafluorethylene channels using Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa. Sterile reverse osmosis (RO) water, and phosphate-buffered saline with and without Tween80 as well as two neutralizing broths (Letheen and Dey-Engley) were each assessed with and without friction. Neutralizer was added immediately after sample collection and samples concentrated using centrifugation. Simulated-use testing was done using TJF-Q180V and JF-140F Olympus duodenoscopes. RESULTS: Despite variability in the bacterial CFU in the BBF model, none of the extraction fluids tested were significantly better than RO. Borescope examination showed far less residual material when friction was part of the extraction protocol. The RO for flush-brush-flush (FBF) extraction provided significantly better recovery of E. coli (p = 0.02) from duodenoscope lever cavities compared to the CDC flush method. DISCUSSION AND CONCLUSION: We recommend RO with friction for FBF extraction of the channel and lever cavity of duodenoscopes. Neutralizer and sample concentration optimize recovery of viable bacteria on culture.

Simulated-Use Polytetrafluorethylene Biofilm Model: Repeated Rounds of Complete Reprocessing Lead to Accumulation of Organic Debris and Viable Bacteria.

OBJECTIVE Biofilm has been implicated in bacterial persistence and survival after endoscope reprocessing. In this study, we assessed the impact of different methods of reprocessing on organic residues and viable bacteria after repeated rounds of biofilm formation when each was followed by full reprocessing. METHODS ATS-2015, an artificial test soil containing 5-8 Log10 colony-forming units (CFU) of Enterococcus faecalis and Pseudomonas aeruginosa, was used to form biofilm in polytetrafluroethylene channels overnight on 5 successive days. Each successive day, full pump-assisted cleaning using bristle brushes or pull-through devices in combination with enzymatic or nonenzymatic detergents followed by fully automated endoscope reprocessor disinfection using peracetic acid was performed. Residuals were visualized by scanning electron microscopy (SEM). Destructive testing was used to assess expected cutoffs for adenosine triphosphate (ATP; <200 relative light units), protein (<2 µg/cm2), and viable bacteria count (0 CFU). RESULTS Protein residuals were above 2 µg/cm2, but ATP residuals were <200 relative light units for all methods tested. Only when enzymatic cleaner was used for cleaning were there no viable bacteria detected after disinfection irrespective of whether bristle brushes or pull-through devices were used. SEM revealed that some residual debris remained after all reprocessing methods, but more residuals were detected when a nonenzymatic detergent was used. CONCLUSIONS Surviving E. faecalis and P. aeruginosa were only detected when the non-enzymatic detergent was used, emphasizing the importance of the detergent used for endoscope channel reprocessing. Preventing biofilm formation is critical because not all current reprocessing methods can reliably eliminate viable bacteria within the biofilm matrix. Infect Control Hosp Epidemiol 2017;38:1284-1290.