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Dutch study on contamination risks from duodenoscopes and linear ultrasound endoscopes

  • In a nationwide study in the Netherlands, a team of experts investigated the prevalence of contaminated duodenoscopes and linear ultrasound endoscopes [2].

  • Contamination occurred regardless of type, age, and use of the endoscopes.

  • Microorganisms of gastrointestinal and oral origin were the most commonly found pathogens.

Contaminated duodenoscopes and linear ultrasound endoscopes may present a risk for the transmission of pathogens. A nationwide study conducted in the Netherlands (henceforth referred to as study 1) from 2018 provided conclusive evidence regarding the prevalence of contaminated duodenoscopes [1]. The authors therefore added a follow-up study (henceforth referred to as study 2), which was published in 2020. This study investigated the prevalence of contaminated duodenoscopes and ultrasound endoscopes, which are similarly designed to duodenoscopes.

159 duodenoscopes and 64 linear ultrasound endoscopes examined

Study 2 included 61 of the facilities in the Netherlands where endoscopic retrograde cholangiopancreatography (ERCP) and/or endosonography (endoscopic ultrasound, EUS) are performed. A total of 159 duodenoscopes were examined. Samples were taken from the same duodenoscope types, manufactured by Olympus, Pentax, and Fujifilm, as in study 1. Depending on the duodenoscope type, four to six sites were sampled. The endoscopy staff performed the sampling in accordance with the video instruction provided. All samples were processed in the same laboratory. In contrast to study 1, study 2 also included the examination of 64 ultrasound endoscopes, with balloon channels in particular also included in the sampling.

Contamination was defined as:

  1. Microbial growth of ≥ 20 colony-forming units (CFUs)/20 ml (any microorganism, abbreviated to AM20)

  2. Presence of microorganisms with gastrointestinal or oral origin, regardless of the CFU count (abbreviated to MGO).

Contamination in all endoscope types

Analysis of the samples revealed contamination in all endoscope types from all manufacturers. According to the AM20 definition, 21 (13%) of duodenoscopes and 8 (13%) of ultrasound endoscopes were contaminated. Microorganisms of gastrointestinal or oral origin were detected in 24 (15%) of duodenoscopes and 9 (14%) of ultrasound endoscopes.

The summarized data from studies 1 and 2 show that a total of 373 duodenoscopes and ultrasound endoscopes were sampled. 62 (17%) of the endoscopes examined were contaminated according to the AM20 definition. MGOs could be detected in 56 (15%) of the endoscopes.

Contamination regardless of age and use

Both studies show that the contamination of duodenoscopes and ultrasound endoscopes did not depend on age and usages. The results suggest that old and more used endoscopes, if properly maintained, exhibit a similar contamination risk to new endoscopes.

Study 2 also demonstrated that the contamination was not dependent on the cleaners and disinfectants used for reprocessing or on the endoscope washer-disinfector (EWD/AER).

Takeaways for practice

The authors conclude from the study results that current reprocessing practices in the Netherlands maybe are unable to guarantee full endoscope decontamination. At the same time, they point out the importance of thorough pre-cleaning and manual cleaning, following the instructions for use (IFU) from the endoscope manufacturer, which were not evaluated in detail in this study but are especially important for the complex distal ends. The authors therefore recommend developing and implementing effective monitoring measures that are easy to apply to check endoscope decontamination.

Discover more about study 1 here: Nationwide systematic survey of duodenoscopes.


  1. Rauwers AW et al. High prevalence rate of digestive tract bacteria in duodenoscopes: a nationwide study, Gut. 2018;67:1637–1645, (accessed on 05/21/2021).

  2. Rauwers AW et al. Nationwide risk analysis of duodenoscope and linear echoendoscope contamination, Gastrointestinal Endoscopy Volume 92, Issue 3, September 2020, Pages 681-69, (accessed on 05/21/2021).