The recent study by Haak et al. on the outbreak of OXA-181-carbapenemase-producing Klebsiella pneumoniae linked to gastrointestinal endoscopy underscores a critical issue in healthcare: endoscope contamination.1 This problem, often attributed solely to duodenoscopes, is now recognized as a broader challenge affecting various types of endoscopes, including gastroscopes and colonoscopes.2 The findings also highlight the role of biofilms in persistent contamination and the urgent need for improved cleaning protocols, particularly in the air-water channels of these instruments.
The study investigated a large outbreak of carbapenem-resistant Klebsiella pneumoniae associated with gastrointestinal endoscopy, including infection control interventions. The early phase of the outbreak was detected in 19 patients, 16 of whom had undergone GI endoscopy. The reprocessing was audited, old endoscopes were replaced by new ones, and systematic microbiological examination of new endoscopes was introduced. After a second round of follow-up, in total, the outbreak strain was isolated from 32 patients and two reprocessed endoscopes.
Beyond Duodenoscopes
While duodenoscopes have been the focus of contamination concerns due to their intricate design, this study contributes to the growing body of evidence that other types of endoscopes are also vulnerable.2 In this particular outbreak, the contamination was not limited to the instrument channels, but was also found in the air-water channels of used colonoscopes as well as new gastroscopes. A full audit was conducted of the facilities reprocessing procedures and found no inadequacies. This finding is alarming as it indicates that even with compliant reprocessing protocols of less complex endoscopes, biofilms can persist and facilitate the transmission of multidrug-resistant organisms.
Air-Water Channels: A Weak Point
The detection of the outbreak strain in the air-water channels of reprocessed endoscopes highlights a potential weak point in current cleaning practices. These channels, due to their narrow diameter, are challenging to clean manually and only receive flushing with a detergent as instructed by the endoscope manufacturer’s instructions for use (IFU). The Haak et al. study findings suggest that residual moisture and organic matter in these channels provide an ideal environment for biofilm formation.1 This underscores the need for targeted cleaning strategies that address these specific areas more effectively.
Cyclic Build-up Biofilm: Representative of the tough biofilm found in clinically used endoscopes
Biofilm found in endoscopes in clinical use is often fixed to the surface from repeated cycles of HLD and drying, meaning mechanical action is critical for its removal.4 Traditional models of biofilm are usually single-organism biofilms that are continuously hydrated, and do not model the growth of biofilm in channels of different diameters.6 Cyclic build-up biofilm is a biofilm model, developed by Alfa and Howie5, and represents the multiple cycles of HLD and drying that can cause biofilm to become fixed. This model is the closest available representation of biofilm isolated from endoscopes in clinical use.
A recent study by Moshkanbaryans et al. showed that manual cleaning with strict IFU adherence failed to remove Cyclic Build-up Biofilm in 1.4 mm channels (the representative diameter of air-water channels).6
Conclusion
The findings from the Haak et al. study should be a wake-up call for the healthcare community. Endoscope contamination is not confined to duodenoscopes and can be significantly influenced by biofilm formation. The presence of biofilm in air-water channels necessitates a shift in cleaning protocols to ensure these critical areas are adequately addressed. Enhanced cleaning methods, regular audits, and possibly redesigning endoscope channels to facilitate better cleaning are possible steps to mitigate the risk of infection transmission. As we advance in medical technology, our infection control practices must evolve to keep pace with these challenges, ensuring patient safety remains paramount.
1 Haak J, Klempien I, Hans JB, et al. Endoscope-associated outbreak of OXA-181-carbapenemase-producing Klebsiella pneumoniae and its implications for hygiene management. J Hosp Infect. Published online 2025. doi:10.1016/j.jhin.2025.01.016
2 Goyal H, Larsen S, Perisetti A, et al. Gastrointestinal endoscope contamination rates – elevators are not only to blame: a systematic review and meta-analysis. Endosc Int Open. 2022;10(06):E840-E853. doi:10.1055/a-1795-8883
3 Primo MGB, Tipple AFV, Costa D de M, et al. Biofilm accumulation in new flexible gastroscope channels in clinical use. Infect Control Hosp Epidemiology. 2022;43(2):174-180. doi:10.1017/ice.2021.99
4 Ribeiro MM, Graziano KU, Olson N, et al. The polytetrafluoroethylene (PTFE) channel model of cyclic-buildup biofilm and traditional biofilm: The impact of friction, and detergent on cleaning and subsequent high-level disinfection. Infect Control Hosp Epidemiology. 2020;41(2):172-180. doi:10.1017/ice.2019.306
5 Alfa MJ, Howie R. Modeling microbial survival in buildup biofilm for complex medical devices. BMC Infect Dis. 2009;9(1):56. doi:10.1186/1471-2334-9-56
6 International Standards Organization. ISO 15883-5:2021 Washer-disinfectors — Part 5: Performance requirements and test method criteria for demonstrating cleaning efficacy. Published online July 2021. https://www.iso.org/standard/68297.html
7 Moshkanbaryans L, Shah V, Tan LY, et al. Comparison of two endoscope channel cleaning approaches to remove cyclic build-up biofilm. J Hosp Infect. 2024;150:91-95. doi:10.1016/j.jhin.2024.05.014
