Organic and bacterial residues on flexible endoscopes: Evaluation of manual cleaning versus automated endoscope reprocessor (AER) cleaning in a clinical setting

BACKGROUND/OBJECTIVE: In a clinical setting, questions regarding whether there are organic and/or bio-residues on cleaned endoscopes are critical and need to be addressed. Visual inspection alone proves difficult due to tiny lumens and the solid black color of endoscopes. Easier methods to visually monitor endoscope cleaning are in great need. In the controlled environment of the laboratory, we tested a technique for potential visual detection of residual proteinaceous material. The purpose of this study is to determine if these results can be applied to the clinical setting. METHODS: In the laboratory, two types of tests were used to evaluate proteinaceous material and bacterial residue on endoscopes that were inoculated with artificial soil and processed in an automated endoscope reprocessor (AER). The first test was an assay for any remaining indicator bacteria. The second test was a visual test using ninhydrin spray reagent (NSR), which turns purple in the presence of protein/amino acids. In a separate study, the visual detection using the NSR technique was applied to a clinical setting. Differences were compared between endoscopes that were manually cleaned and endoscopes processed in an AER with a 5-minute cleaning cycle using an enzymatic detergent. After cleaning, the external surface and endoscope lumen were tested for proteinaceous material using NSR. RESULTS: The laboratory study showed that there was no visual detection of proteinaceous residue and a removal 107 cfu of S. aureus from the test endoscopes after being processed through a cleaning cycle in a an AER. Results obtained on the comparison between manual versus AER cleaning in a clinical setting were similar, with the AER showing a slightly better cleaning ability. However, more sampling will have to be performed to determine which mode of cleaning is statistically better than the other. CONCLUSIONS: The visual detection of proteinaceous residue using NSR has a potential to be an easy mode for monitoring endoscope cleaning.