The present study reviewed a 5-year monthly microbiology endoscopy surveillance and found a low risk of endoscope contamination in our endoscopy unit. Consistent with previous reports, the most common cause of scope contamination was found to be human factors [1, 5, 13, 14]. Despite the complex design of the duodenal scope and recent concerns about duodenal scope contamination [3, 5, 15, 16], duodenal scopes showed a lower scope contamination rate in our study compared with those in previous reports [7, 17, 18] and the frequency of microbiology surveillance should be the same regardless the type of endoscope. A monthly culture of all endoscopes in our unit helped to detect scope contamination and pinpoint the step in the endoscope reprocessing procedure in which contamination occurred.
There are two main methods used to evaluate endoscope contamination after high-level disinfection: non-culture and culture-based methods. The former includes the use of ATP and bioburden testing for point-of-care testing for contamination to measure the performance of manual cleaning [4, 19, 20]. However, this method shows a poor correlation with cultures of fully reprocessed devices  and requires extra work, particularly in a high-volume unit. The microbiological culture of endoscopes is critical to understanding the efficacy of reprocessing and transmission of microorganisms during outbreak investigations [8, 17, 18, 21-23]. However, the existing guidelines are inconsistent in terms of the recommended frequency and method of microbiological monitoring [7, 9, 24] (Table 6). In Europe  and Australia [9, 10], endoscopy microbiology surveillance is regarded as a critical indicator of endoscope reprocessing quality. DEST recommend that microbiology surveillance is performed at a regular frequency . In contrast, the US guidelines recommend against the use of endoscopy microbiology and require more data before a surveillance program should be implemented by healthcare facilities . In the present study, a low risk of scope contamination from various etiologies was identified in the monthly endoscopy surveillance program. Although scope contamination may not be correlated with patient infection, we found this strategy helped early identification of the breach of the reprocessing process before the occurrence of outbreak of scope-related infection.
Many studies have reported a higher rate of duodenal scope contamination [7, 17, 18, 25], and the ESGE recommends a close surveillance interval for duodenal scope compared with that for other types of scopes [1, 7]. Because of increased awareness of the high risk of duodenal scope reprocessing failure and the report of duodenal scope transmitted infection in 2014, our endoscopy staff were trained and audited for duodenal scope reprocessing . The rate of inadequate manual cleaning decreased from 70.4% to 18.8% after auditing the reprocessing process . The present study found a low rate of duodenal scope contamination compared with that of other types of scopes. This may be due to an increased awareness of reprocessing of this specific type of scope within the unit. As prompt identification of contaminated endoscopes is vital to prevent an outbreak of scope transmission, we suggest that monthly microbiology surveillance program should be performed, regardless of the type of endoscope, especially in this era of overemphasizing duodenal scope contamination.
The present study found that human error was the most common cause of scope contamination [26, 27]. Despite established processing guidelines, high rates of non-compliance to the reprocessing process remain [13, 28]. A lack of regular evaluation of reprocessing staff competence (60%) and regular microbiological inspection (56%) [29, 30] in the endoscopy unit was previously shown to result in guideline non-compliance. Education of endoscopy staff was shown to decrease the rate of endoscope contamination after high-level disinfection [19, 27]. In our unit, we performed an annual competence evaluation of endoscopy staff and still failed to eliminate non-adherence to the reprocessing guidelines. In 2018, our unit introduced the Olympus 290 system, which has a different design than the previously used Olympus 260 system. Thus, in 2018, a lack of familiarity with the new system and a mixture of different endoscope modes (Olympus 260 model and Olympus 2290 model ) were attributed to the increased incidence of human error in our endoscopy unit. This obvious challenge in the current endoscopy reprocessing procedures [30-32] was not addressed in the recent endoscopy reprocessing guidelines [1, 2]. A wide variety of devices continually require reprocessing in the endoscopy unit, and technicians need to identify each type, brand, and model of endoscope and apply appropriate reprocessing procedure. Furthermore, complete reprocessing of each endoscope takes up to 40 min , and the technician may speed up the process due to high-volume loads, which may lead to an increased reprocessing error [26, 34]. Memory violation due to too many reprocessing steps, a lack of real-time feedback, and visibility violation were the most causes of human errors during endoscopy reprocessing [32, 35, 36]. Therefore, future studies into endoscopy reprocessing are required to identify the optimal workload for endoscopy technicians, improve the design of endoscopes to simplify and unify the reprocessing procedures, and improve the reprocessing environment to make a safer, more efficient, and more compatible workspace .
The present study has some limitations. Quality control is fundamental to the delivery of safe and efficient endoscopic procedures, and surveillance cultures are an important method; however, the optimal method for sampling and culture incubation periods vary among different countries . We adopted the flush method for microbiology surveillance, as recommended by the DEST guidelines, and the culture recovery rate may be lower than using the flush–brush–flush methods [22, 37]. Furthermore, we did not perform cultures for slow-growing agents such as Mycobacterium. Low scope contamination was found in our study compared with that in previous reports of 12.9% to 71.4% [17, 18, 23, 25], although this may be an underestimation due to the culturing methods used and an incubation period of only 48 h. Since there were no outbreaks of endoscope-related transmission such as CRE infection at our institution, we are not able to evaluate the impact of monthly culturing to prevent scope-related transmission. As culture-negative endoscopes may have clinically significant biological residues, monthly culture monitoring should not replace other infection control methods in the unit. Culturing methods can help to detect flaws in the reprocessing procedure that could increase the risk of transmission of infectious agents in the unit.