Biofilm removal assessed using an AECC and manual cleaning

Microorganisms exist together in intricate structures known as biofilms.¹ Biofilms form in layers that consist of either individual or multiple species of bacteria, along with organic matter.^2,3 Biofilms adhere to surfaces of endoscopes and can protect the contained bacteria from decontamination processes, including cleaning, disinfection, and drying.²

Biofilms pose an infection risk to patients undergoing endoscope procedures, especially if the biofilms include organisms that are resistant to multiple antimicrobial drugs.^4,5 Therefore, the removal of biofilm is crucial for effective disinfection of endoscopes.

For this research, the biofilm was cultivated based on the cyclic-buildup biofilm (CBB) model as described by Ribeiro et al.^6,7 This model replicates biofilm growth through multiple cycles that imitate clinical usage and reprocessing. Growth of CBB was carried out in polytetrafluoroethylene (PTFE) tubing designed to emulate the lumens of endoscope channels with varying inner diameters: 3.7 mm for the suction/biopsy channels, and 1.4 mm for the air-water (AW) and auxiliary (AUX) channels. Modifications to the CBB model enabled biofilm growth in 1.4 mm diameter tubes.⁷

Two different methods of cleaning endoscopes were assessed on their ability to remove CBB in PTFE tubes, representative of endoscope channels: manual cleaning (MC), which follows the endoscope and detergent instructions for use (IFU), and the automated endoscope channel cleaner (AECC), was used according to the manufacturer's IFU. The AECC used a specially formulated cleaning agent which was propelled through the channels at high velocity for cleaning. Measurements of the amount of protein, organic matter, and bacteria left after cleaning were taken, and then compared to the international alert levels (ISO 15883-5:2021).⁷

The AECC was significantly more efficacious than MC in removing CBB markers (protein, total organic carbon [TOC] and viable bacteria) across all types of channels (P<0.001). The AECC lowered protein and total organic carbon (TOC) levels to beneath alert thresholds for inner diameter channels measuring 3.7 mm and 1.4 mm.⁷

Conversely, MC brought protein and TOC below the alert levels in 3.7 mm channels but did not successfully remove these markers from the 1.4 mm channels. Residue levels surpassed the alert thresholds by over 10 times for protein and 3 times for TOC.⁷

There was a significant difference between the AECC and MC in removing viable bacteria from both 3.7 mm and 1.4 mm channels (P<0.001).

Narrow channels such as the AW and AUX channels are not accessible to brushes and in practice are typically not brushed during MC. The research indicates that MC alone is insufficient for thorough cleaning of all endoscope channels, which may help explain the persistence of endoscopy-linked infections reported in the medical literature.⁷

This research is the first to explore CBB removal in narrow diameter channels such as those in gastrointestinal endoscopes. The study highlights the importance of rigorous biofilm models for assessment of cleaning approaches. The CBB model presents a realistic challenge to that which may be present in clinical settings, emphasising the necessity for improved cleaning methods in channels that cannot be brushed.⁷

The AECC introduces a novel approach that allows for the physical cleaning of narrow channel diameters. This study demonstrates its efficacy in cleaning various PTFE channel diameters.

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Disclaimer:

This content is intended for healthcare professionals and is provided for educational and scientific purposes only. It is not intended to be a definitive statement about the subject matter nor is it intended to promote any endoscope channel cleaning product. At the time of writing, the automated endoscope channel cleaner is still under development and has not been approved by regulatory authorities. Certain information in the content relates to protected intellectual property rights owned by Nanosonics or its related companies. While best efforts have been taken, Nanosonics does not make any warranties, representations or undertakings about any of the content (including as to the quality, accuracy, completeness or fitness for any particular purpose of such content) and takes no responsibility for your reliance on the information provided. Any and all use of the information is at your own risk. Healthcare professionals should undertake their own independent enquiries as necessary and exercise professional judgment when assessing their disinfection requirements.