A new buildup biofilm model that mimics accumulation of material in flexible endoscope channels

Microbiological surveillance result of endoscopes after INTERCEPT Foam Spray: a quasi-experimental pilot study in Singapore

BACKGROUND/AIMS

This study aimed to assess the impact of INTERCEPT Foam Spray (IFS) application on delayed endoscope reprocessing through microbiological surveillance culture (MSC).

METHODS

A quasi-experimental, matched-comparison pilot study was conducted using gastrointestinal endoscopy. IFS was applied to the endoscopes after precleaning and before reprocessing the next day. An equal number of endoscopes, matched by endoscope type, were subjected to routine reprocessing. The MSC were subjected to high-level disinfection to detect any contamination. Data were analyzed using the chi-square test or Fisher exact test (categorical data) and Student t-test (continuous data).

RESULTS

In total, 150 MSCs were collected from 42 endoscopes. Positive MSCs were observed in 4.0% (4/75) of the sprayed group and 1.3% (1/75) of the control group (95% confidence interval, 30.34-0.31; p>0.05), all of which were contributed by colonoscopes. Colonoscope were more prone to positive MSC (mean difference in percentage, p<0.05). Mean spraying hours were not associated with detected growth (11.7% vs. 13.6%; 95% confidence interval, 1.43 to -5.27; p>0.05), with environmental and skin flora being the primary contaminants.

CONCLUSIONS

IFS may be applied when delayed endoscope processing is necessary, but with caution when applied to colonoscopes. However, further research is warranted to verify the result.

Comparison of Sampling Methods for Detecting Protein in Gastrointestinal Endoscopes

Background: Persistent microbial contamination of flexible endoscopes has been linked to infections and outbreaks. Valid and reliable sampling methods are critical for monitoring processing effectiveness in flexible endoscopes. In this study, the effectiveness of protein extraction via turbulent fluid flow (TFF) sampling was compared with flush-only sampling in manually cleaned gastrointestinal endoscopes. Methods: A crossover study design, in which both sampling methods were used in alternating order during each endoscope encounter, was utilized to assess protein levels after colonoscopes and gastroscopes underwent manual cleaning. Endoscope channels were sampled with 20 mL sterile water using TFF and flush-only methods. Protein levels were quantified using a spectrophotometer. Results: Protein samples were collected during a total of 40 encounters with 20 unique endoscopes (19 colonoscopes and 21 gastroscopes) following procedural use. More effluent was captured following TFF (20-30 mL) compared with flush-only (19-21 mL) sampling. Zero samples had detectable protein after flush-only sampling, and nine samples (22.5%; two gastroscopes and seven colonoscopes) had detectable protein following TFF sampling (range 1-4 μg/mL). Of those, four exceeded the 2 μg/mL study threshold for recleaning after the first cleaning and three of four dropped to 2 μg/mL or less after recleaning. Conclusion: TFF sampling of the entire suction-biopsy channel allowed the detection of residual protein in nine gastrointestinal endoscopes, whereas no protein was detected in samples obtained by manually flushing the instrument channel. More research is needed to characterize the real-world utility of using the TFF system to verify whether soil and bioburden have been effectively removed during processing. Numerous studies have documented that a majority of fully processed, patient-ready endoscopes harbor microbes.1-8 Microbes found in endoscopes include high-concern organisms (e.g., multidrug-resistant microbes and pathogens) that have been linked to endoscopy-associated outbreaks.9-12 In these outbreaks, visible residual soil was discovered during the outbreak investigation. Current guidelines and standards note that effectively cleaning endoscopes is critical to the success of high-level disinfection (HLD) and sterilization.13,14 Several studies by Ofstead and colleagues6,15,16 have documented high protein levels on endoscopes. A study involving colonoscopes and gastroscopes detected protein on 100% of manually cleaned endoscopes (range 3-11 μg/mL).6 Other studies also found protein in 100% of manually cleaned bronchoscopes (range 2-30 μg/mL) and sterilized ureteroscopes (range 9-32 μg/mL).15,16 These contamination levels were higher than positive controls, which were dirty gastroscopes that had not been manually cleaned. Microbes were found on 12.5% to 60% of fully processed endoscopes, including potential pathogens such as Pseudomonas aeruginosa, Escherichia coli, and Micrococcus luteus.6,15,16 This reinforces the need to verify that endoscopes are clean prior to undergoing HLD or sterilization. Evidence shows that protein can persist through multiple rounds of cleaning.17,18 Despite efforts to clean the endoscope, harvesting samples from surfaces that remain contaminated with soil can be challenging because sampling commonly uses the same tools as cleaning (e.g., brushes or swabs and flushing). Residual soil or bioburden may also be encased in a biofilm matrix that has been hardened through exposure to harsh chemicals used during HLD and/or sterilization and repeated cycles of drying,19,20 thereby increasing the difficulty of capturing a sample. Hervé et al.21 noted that protein deposits in endoscopes were able to resist brushing and flushing, especially in the presence of wear and damage. Historically, flush-only ("flush") sampling was used,22,23 but this method often was limited to the instrument channel and captured lower yields compared with more robust methods.4,24,25 As the effectiveness of sampling affects the validity of results of tests for organic soil and microbial cultures, more robust sampling methods may be required.26 Guidance on sampling for microbial cultures provided by the Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) involves incorporating a brushing step and an additional flushing step ("flush-brush-flush") to dislodge and flush out microbes.27 This method has been found to be more effective than flush sampling,3,24 but brushes cannot access every endoscope channel and may leave behind bristles. Researchers have reported that the FDA/CDC sampling method is cumbersome, time consuming,28 and prone to contamination.7 Even when using recommended sampling methods, investigators have reported needing to rely on external experts and destructive sampling to effectively harvest samples that ultimately revealed the outbreak pathogen.10,11 This underscores the importance of robust sampling methods, both to avoid false negatives from failing to capture soil or bioburden that is present and to avoid false positives from environmental contamination.7,29 Given the challenges associated with current sampling techniques for organic soil testing and microbial cultures, this study was conducted to evaluate a method that could potentially improve sample validity and reduce the influence of human factors on sampling. The automated turbulent fluid flow (TFF) system pumps a mixture of air and water through the suction and instrument channels from the suction connector to the distal end and into a sterile collection cup that is sealed during sampling to maintain a closed system. The turbulent flow provides friction to endoscope interior surfaces without needing to use a brush.30 In this study, protein extraction via TFF sampling was compared with flush sampling in manually cleaned gastrointestinal endoscopes.

Effect of a novel endoscope cleaning brush on duodenoscope contamination

BACKGROUND

Current duodenoscope reprocessing protocols are insufficient to prevent contamination and require adaptations to prevent endoscopy-associated infections (EAIs). This study aimed to investigate the effect of a new endoscope cleaning brush on the contamination rate of ready-to-use duodenoscopes.

METHODS

This retrospective before-and-after intervention study collected duodenoscope surveillance culture results from March 2018 to June 2022. Contamination was defined as ≥1 colony-forming unit of a microorganism of gut or oral origin (MGO). In December 2020, an endoscope cleaning brush with a sweeper design was introduced as an intervention in the manual cleaning of duodenoscopes. A logistic mixed-effects model was used to study the effects of this intervention.

RESULTS

Data were collected from 176 culture sets before the new brush's introduction and 81 culture sets afterwards. Pre-introduction, culture sets positive with an MGO comprised 45.5% (95%CI 38.3%-52.8%; 80/176), decreasing to 17.3% (95%CI 10.6%-26.9%; 14/81) after implementation of the new brush. Compared with the former brush, duodenoscopes cleaned with the new brush had lower odds of contamination with MGOs (adjusted odds ratio 0.25, 95%CI 0.11-0.58; P=0.001) CONCLUSIONS: Use of the new brush in manual cleaning reduced contamination with MGOs and is expected to prevent EAIs. These findings should be confirmed in future prospective randomized studies.

Biofilm on and structural damage of rotary cutting instruments after 5 cycles of clinical use and processing

BACKGROUND

Rotary cutting instruments (RCIs) are sterilized routinely. The authors aimed to analyze the structural integrity, presence of dirt, and microbial contamination of RCIs used in clinical practice after processing.

METHODS

Eighty-four RCIs (42 carbide burs, 42 diamond burs) were divided into baseline, control, and test groups. The RCIs were evaluated by means of scanning electron microscopy and microbiological analysis. Evaluation criteria included presence of structural damage, dirt, biofilm, and isolated cells and their phenotypic profile.

RESULTS

The carbide burs from all groups and diamond burs from the test groups had structural damage. Dirt was observed in the baseline and test groups. Three bacterial species were isolated from 4 RCIs (9.52%). An isolated cell was observed from 1 carbide bur. Biofilm was observed on 3 RCIs (7.14%).

CONCLUSIONS

RCIs should not be subjected to multiple uses; after the first clinical use they accumulate structural damage and dirt that hampers the cleaning step, causing failure in the sterilization process.

PRACTICAL IMPLICATIONS

The presence of microorganisms and structural damage on the RCIs confirmed that they are not amenable to processing, a fact that characterizes them as a single-use health care product.

A dynamic flow model mimicking duodenoscope reprocessing after bacterial contamination for translational research

OBJECTIVE

Duodenoscopy-associated infections and outbreaks are reported globally despite strict adherence to duodenoscope reprocessing protocols. Therefore, new developments in the reprocessing procedure are needed.

DESIGN

We evaluated a novel dynamic flow model for an additional cleaning step between precleaning and manual cleaning in the reprocessing procedure.

METHODS

A parallel plate flow chamber with a fluorinated ethylene propylene bottom plate was used to mimic the duodenoscope channels. The flow chamber was inoculated with a suspension containing Klebsiella pneumoniae to simulate bacterial contamination during a duodenoscopic procedure. After inoculation the flow chamber was flushed with a detergent mimicking precleaning. Subsequently the flow chamber was subjected to different interventions: flow with phosphate-buffered saline (PBS), flow with 2 commercial detergents, flow with sodium dodecyl sulfate with 3 different concentrations, and flow with microbubbles. Adhering bacteria were counted using phase-contrast microscopy throughout the experiment, and finally, bacterial viability was assessed.

RESULTS

During precleaning both PBS and 1% (v/v) Neodisher Mediclean Forte were able to desorb bacteria, but neither proved superior. After precleaning only sodium dodecyl sulfate could desorb bacteria.

CONCLUSIONS

Flushing during precleaning is an essential step for reducing adhering luminal bacteria, and sodium dodecyl sulfate is a promising detergent for bacterial desorption from duodenoscope channels after precleaning.

Mild Positive Pressure Improves the Efficacy of Benzalkonium Chloride against Staphylococcus aureus Biofilm

Current protocols using liquid disinfectants to disinfect heat-sensitive hospital items frequently fail, as evidenced by the continued isolation of bacteria following decontamination. The contamination is, in part, due to biofilm formation. We hypothesize that mild positive pressure (PP) will disrupt this biofilm structure and improve liquid disinfectant/detergent penetration to biofilm bacteria for improved killing. Staphylococcus aureus biofilm, grown on polycarbonate coupons in the biofilm reactor under shear at 35 °C for 3 days, was treated for 10 min and 60 min with various dilutions of benzalkonium chloride without PP at 1 atmosphere (atm), and with PP at 3, 5, 7, and 10 atm. The effect on biofilm and residual bacterial viability was determined by standard plate counts, confocal laser scanning microscopy, and scanning electron microscopy. Combined use of benzalkonium chloride and PP up to 10 atm significantly increased biofilm killing up to 4.27 logs, as compared to the treatment using disinfectant alone. Microscopy results were consistent with the viability plate count results. PP improved disinfectant efficacy against bacterial biofilm. The use of mild PP is possible in many flow situations or if equipment/contaminated surfaces can be placed in a pressure chamber.

Duodenoscope-associated infections: a review

Flexible digestive endoscopes are used for the management of various conditions with hundreds of thousands of therapeutic procedures performed worldwide each year. Duodenoscopes are indispensable tools for the delivery of minimally invasive vital care of numerous pancreaticobiliary disorders. Despite the fact that nosocomial infections after endoscopic retrograde cholangiopancreatography (ERCP) have always been among the most frequently cited postprocedural complications, recent emergence of duodenoscope-transmitted multiple drug-resistant bacterial infections has led to intense research and debate yet with no clearly delineated solution. Duodenoscope-transmitted nosocomial infections have become one of the most visible topics in the recent literature. Hundreds of high-impact articles have therefore been published in the last decade. This review article discusses how such infections were seen in the past and what is the current situation in both research and practice and thus tries to solve some of the unanswered questions for the future. With the persistence of nosocomial infections despite strict adherence to both manufacturer-issued reprocessing protocols and international guidelines and regulations, an urgent and proper microbiologically driven common action is needed for controlling such nosocomial worldwide threat.

Biofilms on instruments and environmental surfaces: Do they interfere with instrument reprocessing and surface disinfection? Review of the literature

There is a growing appreciation for the role of biofilm-embedded microbes in many different aspects of infection transmission. The format of biofilm includes traditional hydrated biofilm, build-up biofilm, and dry surface biofilm. The objectives of this article are to discuss how traditional biofilm differs from build-up biofilm and dry surface biofilm, and to review the evidence supporting infection transmission from biofilm that accumulates in reprocessed instruments and from dry biofilm that forms environmental reservoirs.

Safely reprocessing duodenoscopes: current evidence and future directions

Highly publicised outbreaks of various infections related to the use of duodenoscopes have increased public awareness of the once arcane and largely ignored subject of endoscope reprocessing. Since 2015, national professional societies, multiple federal agencies, and even the US Senate have written reports and guidelines on duodenoscope reprocessing. However, their recommendations are sometimes contradictory and difficult to implement, and new research on the topic is published regularly which further complicates the situation. With this flood of new and sometimes contradictory information, clinicians can feel confused about how to assure the safety of their patients undergoing duodenosocopy. This Review summarises the most salient current research on duodenoscope-associated outbreaks and reprocessing, and aims to provide clinicians with practical information applicable to their practice.

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.

A novel polytetrafluoroethylene-channel model, which simulates low levels of culturable bacteria in buildup biofilm after repeated endoscope reprocessing

BACKGROUND AND AIMS

Clinical studies have shown variable culture results from flexible endoscope channels possibly because of low levels of bacteria that are difficult to extract. The aim of this study was to develop a simulated-use buildup biofilm (BBF) model that mimics low levels of viable bacteria after repeated rounds of aldehyde fixation and accumulation.

METHODS

New endoscope channels were exposed to 8 days of repeated rounds of biofilm formation using ATS2015 containing Enterococcus faecalis and Pseudomonas aeruginosa, rinsing, fixation with glutaraldehyde, and rinsing. Viable count and scanning electron microscopy and borescope examination were used to compare the impact of dry storage over 26 weeks on the level of culturable bacteria and to compare the Centers for Disease Control and Prevention flush method of channel harvesting with a flush-brush-flush method.

RESULTS

E faecalis (log₁₀ 6.6) and P aeruginosa (log₁₀ 8.6) accumulated over 8 days of cyclic biofilm formation and partial glutaraldehyde fixation, but after a final exposure to 2.6% glutaraldehyde the level of culturable bacteria was less than 2 log₁₀. The Centers for Disease Control and Prevention channel harvesting method appeared by borescope to be inferior to a flush-brush-flush sample collection method for detection of viable bacteria. P aeruginosa increased up to 7 log₁₀ after 26 weeks of dry storage, indicating there were viable but nonculturable bacteria present initially that recovered during storage.

CONCLUSIONS

Viable but nonculturable P aeruginosa within the BBF model are able to recover, and this phenomenon may explain the variability of culture in patient-used endoscopes. Our data also indicated that friction may be a critical part of sample collection from endoscope channels.

Infectious complications in gastrointestinal endoscopy and their prevention

Gastrointestinal endoscopes are medical devices that have been associated with outbreaks of health care-associated infections. Because of the severity and limited treatment options of infections caused by multidrug-resistant Enterobacteriaceae and Pseudomonas aeruginosa, considerable attention has been paid to detection and prevention of these post-endoscopic outbreaks. Endoscope reprocessing involves cleaning, high-level disinfection/sterilization followed by rinsing and drying before storage. Failure of the decontamination process implies the risk of settlement of biofilm producing species in endoscope channels. This review covers the infectious complications in gastrointestinal endoscopy and their prevention and highlights the problem of infection risk associated with different steps of endoscope reprocessing.