Antimicrobial decontamination of endoscopes: Are we there yet?

The growth of GI endoscopy provision globally has mirrored developments in the management of GI disease. Endoscopic procedures have become increasingly complex and are often performed in critically ill patients. All endoscopes have the potential to harbor and transmit pathogens, which could cause lethal healthcare-associated infections (HAIs). Data from the Centers for Disease Control and Prevention (CDC) suggest that the prevalence of HAIs has been on the decline. Endoscopy is generally safe, and HAIs associated with endoscopy have been uncommon despite the volume of procedures performed annually. The prevalence of endoscopy-associated infections (EAIs) is difficult to estimate, with a historical 1993 American Society for Gastrointestinal Endoscopy (ASGE) position paper suggesting that this was 1 in 1.8 million procedures, although Ofstead et al suggested that this figure was closer to 1 in 276,000. A different ASGE estimate in 2006 using the same methods suggested that the prevalence of EAIs was probably around 1 in 10 million procedures.^{,  ,}  Each instance of EAI has been associated with a breach in endoscope cleaning and disinfection guidelines. There has been much scrutiny over recent years on outbreaks of EAIs associated with Carbapenem-resistant Enterobacteriaceae (CRE) and deaths related to duodenoscopes. A recent ASGE update on guidelines on reprocessing GI endoscopes has emphasized the importance of following the endoscope manufacturer’s instructions on cleaning and reprocessing. Duodenoscopes are particularly challenging in terms of cleaning owing to the complexity of the parts involved, with the elevator channel unit thought to pose a part that is specifically difficult to disinfect thoroughly. Moreover, most endoscopy units see a high throughput of endoscopes every day because of the demand for GI endoscopy procedures. Is the current level of guidance on reprocessing of GI endoscopes adequate to reduce the risk of EAIs? Can we assure the public that the current level of disinfection of GI endoscopes is adequate?

The article by Singh et al in this issue of Gastrointestinal Endoscopy tries to address this question for duodenoscopes. In this study, they meticulously perfused the suction and elevator channels of 3 Olympus duodenoscope models (JF-140F, TJF-160V, and TJF-180V) with an inoculum of Escherichia coli and Enterococcus faecalis in an artificial test soil medium (ATS2015) containing albumin, hemoglobin, carbohydrates, mucin, cellulose, and lipids (ie, contaminants likely to remain on the endoscopes after clinical use). The test soil and bacterial suspension were applied to the endoscope suction channel and the guidewire channel (including the elevator). This suspension was additionally applied behind the elevator lever. After inoculation, each endoscope was reprocessed in an automated reprocessor (AER) according to 3 different cleaning protocols (protocol 1, cleaning according to manufacturer’s instructions; protocol 2, similar to protocol 1 with the addition of an alcohol flush after reprocessing; and protocol 3, similar to protocol 1 with the addition of a channel flush during the cleaning and rinsing stages of reprocessing). Samples were then acquired from each endoscope from different parts (elevator channel, elevator lever, lever cavity using sterile reverse osmosis water and the instrument channel) after the endoscopes had been reprocessed and dried in a channel-purge cabinet (10-minute air purge through all endoscope channels every 30 minutes). The authors then tested these samples for adenosine triphosphate (ATP), which could represent residuals from patient secretions and bacteria. Because high levels of bacterial residuals are required to elicit a positive ATP reading, the test is considered, despite its obvious caveats in not being able to distinguish the source of the ATP levels, to be a useful marker for the endoscope cleaning process. Samples were then cultured on blood agar plates, and as per the CDC protocol, cultures containing >100 colony-forming units (CFU) of bacteria were considered “actionable.”

The authors found that despite adherence to the manufacturer’s recommendations for endoscope cleaning and reprocessing, “actionable” levels of bacteria were seen in samples acquired after all 3 cleaning protocols. Protocols 2 and 3 (alcohol flush and extra rinsing) did not seem to offer any additional advantage over protocol 1 (manufacturer’s recommendations). Encouragingly, no enteric Gram-negative bacteria were detected in cultures of the samples. Interestingly, the authors found an increase in the bacterial counts over a period of time after reprocessing, suggesting that there may be an issue with bacterial biofilm development and microbial buildup after reprocessing. This could have potential implications about the duration of storage before re-use.

So, what does this study tell us? It reassures us and provides the general public with the confidence that the current high-level disinfection endoscope cleaning and reprocessing systems are sufficient to eradicate enteric Gram-negative organisms, as long as the cleaning instructions are followed robustly. A strong oversight on quality control by external regulators and local processes should ensure the reliability of reprocessing mechanisms.^, 

The authors note that non–Gram-negative enteric organisms such as Staphylococcus aureus, β-hemolytic streptococci, and yeasts should also be considered actionable if found on endoscopes. An important point the authors raise is that any culture of ≥100 CFU of low- or moderate-concern bacteria should be actionable because this may be indicative of suboptimal endoscope reprocessing. The presence of low-concern bacteria (Micrococcus species, coagulase-negative staphylococci, Bacillus species, diphtheroids, or other Gram-positive bacteria) on a duodenoscope is generally associated with environmental contamination. However, moderate-concern bacteria (commensal Neisseria species, viridans group streptococci, Moraxella species) are found in the oral cavity, and the presence of these species on a duodenoscope should be considered to represent a failure of cleaning and reprocessing protocols.

How frequently should antimicrobial surveillance be conducted, and is it feasible in a busy endoscopy unit? There is variation and inconsistency in guidance and practice across the world. The European Society of Gastrointestinal Endoscopy and European Society of Gastroenterology Endoscopy Nurses and Associates, the British Society of Gastroenterology, and the Gastroenterological Society of Australia guidelines recommend routine antimicrobial sampling of AER rinse water at varying frequencies.^{,  ,} 

Although there are no recommendations for routine antimicrobial sampling in endoscopy units in the United States, rigorous testing is mandated when nosocomial infections are suspected. Issues with routine antimicrobial culturing include practical difficulties for endoscopy centers with no access to microbiological facilities, slow turnaround time for endoscopes after sampling, and that viruses such as hepatitis C and human immunodeficiency virus cannot be cultured with routine culture methods. However, these issues should not detract from the real concerns about endoscope contamination generated by Singh et al. The increase in bacterial counts observed in their study 72 hours after reprocessing raises an additional concern about the optimal duration of dry storage after reprocessing, and additional work is necessary in this area.

There is thus need for an international task force incorporating representations from gastroenterological societies and industry to examine this issue and arrive at a consensus on antimicrobial sampling and surveillance of GI endoscopes with associated basic regulation in this area. This may need additional support from governments because a universal system of routine checks will have associated cost implications. However, as professionals, we owe it to the public to maintain safe and effective systems across the world with commonality in basic safety assessments. After all, would we not expect these standards ourselves should we need a GI endoscopy procedure?