Post written by Koen van der Ploeg, MD, MSc, from the Department of Gastroenterology and Hepatology and the Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center, Rotterdam, The Netherlands.

Endoscopes are exposed to a high load of GI flora during endoscopic procedures. Consequently, an extensive reprocessing protocol, including high-level disinfection, is performed after each procedure.

Despite these measures, endoscopes may remain contaminated with patient flora, posing a risk of transmitting microorganisms to subsequent patients. This issue is particularly pronounced in high-risk endoscopes, such as duodenoscopes, which have been implicated in outbreaks.

To identify contaminated devices, international guidelines recommend regular microbiological surveillance. This involves sampling and culturing various endoscope components, including the biopsy and suction channels and distal tip. If an endoscope is found to be contaminated, it is quarantined and subjected to repeated reprocessing and culturing until it yields negative results. Our study aimed to evaluate the sensitivity of current sampling and culturing methods and to estimate the prevalence of contaminated duodenoscope use.

Duodenoscope culturing is the only method available for detecting bacterial contamination. However, evidence from outbreak reports and laboratory studies suggests that the sensitivity of current sampling and culturing methods is not absolute. As a result, a single false-negative culture result could prematurely clear a contaminated endoscope for clinical use, posing a significant risk to patient safety.

Given this concern, we sought to assess the sensitivity of contamination detection in a real-world setting and to quantify the number of procedures performed with contaminated duodenoscopes. This would provide insights into the magnitude of the problem and inform whether further interventions are necessary.

Our study analyzed 556 duodenoscope cultures collected over 7 years of microbiological surveillance, identifying contamination with microorganisms of gut or oral origin in 185 cultures (33.3%). We identified instances where individual duodenoscopes remained contaminated over extended periods. Using whole genome sequencing, we confirmed the genetic relatedness of microorganisms in some cases, revealing patterns of intermittent false-negative culture results between positive findings. Based on these observations, we determined that the sensitivity of culturing methods ranged from 82.2% to 98.9%.

By integrating these findings with duodenoscope usage data, we estimated that 12.3% to 23.7% of procedures were performed using contaminated duodenoscopes. These results underscore the ongoing issue of duodenoscope contamination and highlight the limited sensitivity of current detection methods, which can result in premature clearance of contaminated devices from quarantine.

Our findings call into question the adequacy of relying on a single negative culture result to declare a quarantined duodenoscope safe for clinical use. We recommend re-evaluating this practice to mitigate the risk of patient harm. In addition, research should focus on improving the sensitivity of detection methods.

Timeline illustration of the clusters. Black rectangles indicate duodenoscope use. All Pseudomonas aeruginosa isolates within the individual clusters were genetically related.

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