---
title: "Microbiological surveillance after automated reprocessing of GI endoscopes: randomized comparison"
id: "plos-one-5-microbiological-surveillance-after-automated-reprocessing-of-gastrointestinal"
canonical_url: "https://medichelpline.com/clinical-feed/plos-one-5-microbiological-surveillance-after-automated-reprocessing-of-gastrointestinal"
content_type: "clinical_feed_article"
specialty: "Infectious Disease"
source_name: "PLOS ONE (Medicine)"
source_url: "https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0360048"
published_at: "2026-10-06T14:00:00.000Z"
evidence_level: "Journal Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# Microbiological surveillance after automated reprocessing of GI endoscopes: randomized comparison
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/plos-one-5-microbiological-surveillance-after-automated-reprocessing-of-gastrointestinal
- **Specialty:** [Infectious Disease](https://medichelpline.com/clinical-feed/infectious-disease.md)
- **Primary Source:** PLOS ONE (Medicine)
- **Source URL:** [Original Journal Publication](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0360048)
- **Published At:** 2026-10-06T14:00:00.000Z
- **Evidence Rating:** Journal Feed
## Executive GIST (TL;DR)
- This was an exploratory single-center, prospective randomized microbiological surveillance study of 222 patient-used forward-viewing upper and lower gastrointestinal endoscope-use episodes allocated 1:1:1 to three automated endoscope reprocessor (AER) systems: **peracetic acid (PAA)**-based AER, **ozonated water** AER, and **strongly acidic electrolyzed water** AER. - All episodes underwent standardized bedside pre-cleaning and manual cleaning before automated reprocessing; post-reprocessing samples were taken from predefined external and internal sites prior to alcohol flushing, drying, or storage. - Primary endpoint (surveillance success) required ≤20 colony-forming units (CFU) per sample at all sampled sites and absence of predefined indicator organisms (E. coli, enterococci, Enterobacteriaceae, Pseudomonas aeruginosa and other gram-negative nonfermenters, Staphylococcus aureus, Staphylococcus epidermidis). - Surveillance success rates: **PAA** 71/74 (95.9%), **ozonated water** 71/74 (95.9%), **strongly acidic electrolyzed water** 67/74 (90.5%). - Risk differences versus PAA: strongly acidic electrolyzed water −5.4 percentage points (95% CI −14.6 to 3.2); ozonated water 0.0 percentage points (95% CI −7.7 to 7.7). - Post hoc non-inferiority analyses using a −5 percentage-point margin did not demonstrate non-inferiority for either functional-water system; a −10 percentage-point margin supported ozonated water but not strongly acidic electrolyzed water. - Post hoc scope-level sensitivity analyses were directionally consistent with the primary analysis and indicated that repeated failures in a single physical endoscope influenced results. - The study was pragmatic and not powered for definitive non-inferiority; registration in UMIN-CTR was retrospective. Findings are presented as microbiological quality-assurance data, not direct evidence of clinical infection risk or comparative clinical effectiveness.
## Clinical Analysis & Structured Key Points
Microbiological surveillance after automated reprocessing of gastrointestinal endoscopes in routine clinical practice: A prospective randomized microbiological surveillance study | PLOS One Browse Subject Areas ? Click through the PLOS taxonomy to find articles in your field. For more information about PLOS Subject Areas, click here . Article Authors Metrics Comments Media Coverage Reader Comments Figures Figures Abstract Microbiological surveillance is used to monitor the quality of gastrointestinal endoscope reprocessing, but prospective data comparing automated endoscope reprocessor systems under routine workflow conditions remain limited. We conducted an exploratory, single-center, prospective randomized surveillance study of 222 endoscope-use episodes involving patient-used forward-viewing upper and lower gastrointestinal endoscopes. Endoscope-use episodes were allocated 1:1:1 to strongly acidic electrolyzed water, ozonated water, or peracetic acid using an Excel-generated random-number procedure (n = 74 each). Assigned reprocessing was performed after standardized bedside pre-cleaning and manual cleaning. Post-reprocessing samples were obtained from predefined external and internal sites. Surveillance success was defined as ≤20 colony-forming units per sample at all sampled sites and absence of predefined indicator organisms. Success was achieved in 67/74 (90.5%) strongly acidic electrolyzed-water episodes, 71/74 (95.9%) ozonated-water episodes, and 71/74 (95.9%) peracetic-acid episodes. Risk differences in surveillance success versus peracetic acid were −5.4 percentage points (95% confidence interval, −14.6 to 3.2) and 0.0 percentage points (95% confidence interval, −7.7 to 7.7), respectively. In exploratory post hoc non-inferiority analyses using a −5 percentage-point margin, non-inferiority was not demonstrated for either functional-water system. A −10 percentage-point margin supported ozonated water but not strongly acidic electrolyzed water. Post hoc scope-level sensitivity analyses were directionally consistent with the primary analysis and highlighted the influence of repeated failures in an individual physical endoscope. These findings should be interpreted as exploratory microbiological quality-assurance data, not as evidence of clinical infection risk or comparative clinical effectiveness. Study registration: University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR), UMIN000061627 (registered May 19, 2026; enrollment began November 8, 2024). Citation: Kato M, Hayashi H, Hironaka N, Chiba M, Abe T, Shimamoto N, et al. (2026) Microbiological surveillance after automated reprocessing of gastrointestinal endoscopes in routine clinical practice: A prospective randomized microbiological surveillance study. PLoS One 21(10): e0360048. https://doi.org/10.1371/journal.pone.0360048 Editor: Banreet Singh Dhindsa, University of Nebraska Medical Center College of Medicine, UNITED STATES OF AMERICA Received: July 22, 2026; Accepted: September 21, 2026; Published: October 6, 2026 Copyright: © 2026 Kato et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: All relevant data underlying the findings of this study are provided within the paper and its Supporting Information files, including the anonymized endoscope-level dataset, the plot-ready dataset underlying the figures, the summary table workbook, and the complete R code used for the analyses. Potentially identifying patient-level information has been removed from the publicly available datasets to protect participant privacy. A table listing all 13 protocol-defined surveillance-failure episodes is provided as Supporting Information ( S5 Table ). Funding: This study received non-monetary in-kind support from Kaigen Pharma Co., Ltd. and IHI Logistics & Machinery Corporation through the temporary loan of automated endoscope reprocessing systems and technical support related to their operation and performance. No monetary grant, study-related salary support, honoraria, or other financial compensation was provided to the authors for this work, and no grant number applies. HH and NH, employees of the respective companies, participated in sample collection and provided technical support related to the reprocessing systems. The funders had no role in the study design, microbiological testing, statistical analysis, interpretation of the results, decision to publish, or preparation of the manuscript. The specific roles of HH and NH are described in the Author Contributions section. Competing interests: This study received non-monetary in-kind support from Kaigen Pharma Co., Ltd. and IHI Logistics & Machinery Corporation through the temporary loan of automated endoscope reprocessing systems and technical support related to their operation and performance. HH is an employee of Kaigen Pharma Co., Ltd., and NH is an employee of IHI Logistics & Machinery Corporation. HH and NH participated in sample collection and provided technical support related to the reprocessing systems. No author received any study-related salary, honorarium, research grant, or other monetary compensation from either company. The supporting companies had no additional role in the study design, microbiological testing, statistical analysis, interpretation of the results, decision to publish, or preparation of the manuscript. This does not alter our adherence to PLOS ONE policies on sharing data and materials. Introduction Flexible gastrointestinal endoscopes are semi-critical medical devices that contact mucous membranes and can be exposed to blood, intestinal contents, and other potentially infectious material during routine clinical use. Inadequate cleaning, disinfection, drying, or storage has been associated with healthcare-associated infections and outbreak events, particularly when device complexity or workflow deviations compromise reprocessing [ 1 – 5 ]. Reliable, reproducible reprocessing is therefore a central component of infection prevention in gastrointestinal endoscopy units. Current guidance emphasizes a standardized multistep workflow that includes bedside pre-cleaning, meticulous manual cleaning with detergent flushing and channel brushing, high-level disinfection, rinsing, drying, and appropriate storage [ 1 , 2 ]. Peracetic acid (PAA)-based automated endoscope reprocessors (AERs) are widely used because PAA has broad antimicrobial activity under validated conditions. However, real-world microbiological performance depends on the entire reprocessing chain, including manual cleaning, endoscope design, AER cycle execution, staff adherence, drying, storage, and sampling sensitivity. Microbiological surveillance provides a practical quality-assurance approach for assessing residual bioburden after reprocessing. Surveillance programs use quantitative culture thresholds and predefined indicator organisms to identify possible process deviations; they do not directly estimate patient-level infection incidence or prove absolute reprocessing safety [ 6 – 9 ]. Functional-water AER systems, including strongly acidic electrolyzed water and ozonated water, have been introduced in some clinical settings. These systems differ in generation method, active antimicrobial species, stability, delivery to internal channels, and process-control mechanisms. Prior clinical and experimental studies have evaluated electrolyzed acid water for endoscope reprocessing [ 10 , 11 ]. Importantly, a recent multicenter study in otorhinolaryngological endoscopy reported that electrolyzed acid water substantially reduced bacterial contamination after clinical use and supported its feasibility for less complex flexible endoscopes [ 12 ]. Whether such findings can be generalized to gastrointestinal endoscopes remains uncertain because gastrointestinal endoscopes have different contamination burdens, longer and more complex channels, and distinct clinical workflows. Accordingly, we conducted an exploratory prospective randomized surveillance study to evaluate microbiological quality-assurance outcomes after reprocessing patient-used gastrointestinal endoscopes with two functional-water systems and a PAA-based system under routine clinical workflow conditions. The objective was not to demonstrate clinical infection prevention or device interchangeability, but to provide transparent, endoscope-level surveillance data that could inform quality-management programs and future confirmatory studies. Materials and methods Study design, ethics, and registration This exploratory prospective randomized surveillance study was conducted at a single tertiary-care endoscopy center under routine clinical workflow conditions. The Institutional Review Board of The Jikei University School of Medicine approved the study protocol (No. 36–199; 12308). Enrollment began on November 8, 2024. The study was registered in the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR; UMIN000061627) on May 19, 2026 and publicly released on May 20, 2026; the registration was therefore retrospective. All patients received an oral explanation of the study from a physician at the bedside before participation. A nurse was present during the consent process and documented the verbal consent in the electronic medical record. This oral consent and medical-record documentation procedure was approved by the Institutional Review Board. The study complied with the ethical principles of the Declaration of Helsinki. The unit of allocation was the endoscope-use episode. Allocation was based on the scheduled examination list available on the preceding day, and the assigned reprocessing method was applied after completion of the clinical examination and standardized manual cleaning. The allocated intervention was an endoscope reprocessing method applied to the patient-used endoscope in that episode, and the outcome was a microbiological surveillance result rather than a patient health outcome. Therefore, the study is reported as a prospective randomized microbiological surveillance study rather than as a clinical trial designed to assess patient outcomes. Endoscopes and reprocessing workflow Consecutive endoscope-use episodes involving patient-used forward-viewing upper and lower gastrointestinal endoscopes were included. Endoscope type and procedural factors, including biopsy, therapeutic intervention, and known viral infection status, were recorded from endoscopy reports and medical records. Diagnostic examination only was defined as an examination without biopsy or therapeutic intervention. Eligible units were endoscope-use episodes involving patient-used flexible gastrointestinal endoscopes used for routine gastrointestinal endoscopic examination or treatment. Exclusion criteria were: (1) patients with prion disease and endoscopes used in such patients; (2) minors and endoscopes used in minors; (3) patients who declined study participation and endoscopes used in those patients; (4) endoscopes with leakage detected during the pre-disinfection leak test; and (5) cases considered inappropriate for inclusion by the principal investigator or study investigators. After each examination, bedside pre-cleaning was performed immediately, followed by standardized manual cleaning with detergent flushing and channel brushing according to guidance for flexible gastrointestinal endoscope reprocessing [ 1 , 2 ]. Endoscope-use episodes were allocated to the three AER systems in a 1:1:1 ratio using the computer-generated random-number procedure specified in the study protocol. Using the list of scheduled endoscopic examinations available on the preceding day, random numbers were generated with the RAND function in Microsoft Excel. The list was sorted in descending order of these random numbers and divided into three parts: the first third was assigned to KD-1, the second third to OED, and the final third to PAA. After manual cleaning, each eligible endoscope underwent automated reprocessing with its assigned AER system. Personnel performing reprocessing and sample collection were not blinded to allocation. The external microbiological laboratory was not provided with AER allocation information and performed microbiological testing without knowledge of the assigned reprocessing system. The three AER systems were KD-1 (Kaigen Pharma Co., Ltd., Osaka, Japan), which uses strongly acidic electrolyzed water; OED (IHI Logistics & Machinery Corporation, Tokyo, Japan), which uses ozonated water; and OER-6 (Olympus Corporation, Tokyo, Japan), a PAA-based system. Each AER was operated according to the manufacturer’s validated cycle conditions. Cycle parameters were not experimentally modified, preserving a pragmatic routine-practice comparison. Microbiological sampling and culture Microbiological sampling was performed at two time points: immediately after completion of the examination before bedside pre-cleaning, and immediately after completion of the AER cycle. Post-reprocessing samples were collected before alcohol flushing, drying, or storage. For surface sampling, a microbiological swab moistened with sterile saline was used to wipe the entire insertion portion (site D) or the entire control section (site E) 10 times; a fixed surface area in cm 2 was therefore not specified. For channel sampling (site F), 20 mL of sterile saline was flushed through the biopsy port, and the recovered fluid was collected at the distal forceps-channel outlet and submitted for microbiological culture. No neutralizing agent was used in the sampling or transport medium. Samples were processed by an external microbiology laboratory (Japan Microbiology Clinic Co., Ltd., Tokyo, Japan). Quantitative aerobic bacterial culture was performed using soybean-casein digest (SCD) agar, with incubation at 35 °C for 48 h. Colony-forming units (CFU) were counted visually and reported as CFU per sample. Organisms were identified by 16S rDNA sequence analysis. Culture results were recorded separately according to sampling method, sampled site, and time point. Raw culture reports included exact CFU counts and categorical results such as “below detection limit” or “ < 20 CFU.” For endpoint classification, all results reported below the laboratory reporting threshold were classified as below the predefined CFU failure threshold. For descriptive numeric summaries and figures, results below the reporting threshold were coded as 0 CFU, while the original raw reporting categories were retained in the shared dataset. Outcomes The primary outcome was microbiological surveillance success for each endoscope-use episode after automated reprocessing. Success was defined as both residual bacterial load ≤20 CFU per sample at every sampled site and absence of predefined indicator organisms after reprocessing. Indicator organisms were predefined in the study protocol as Escherichia coli , enterococci, members of the Enterobacteriaceae, Pseudomonas aeruginosa and other gram-negative nonfermenters, Staphylococcus aureus , and Staphylococcus epidermidis . Detection of any predefined indicator organism was classified as surveillance failure irrespective of the CFU count. Secondary outcomes included the distribution of CFU counts, failure components, and the distribution of failures according to endoscope type, sampling method, sampled site, procedural factor, individual endoscope identifier, and available repair history. Sample size and statistical analysis Because robust preliminary data were unavailable for surveillance-based microbiological outcomes comparing these AER systems under routine workflow conditions, the sample size of 74 endoscope-use episodes per group was determined by feasibility during the predefined study period and the expected number of eligible routine endoscopic procedures at our institution. The study was therefore not powered for a definitive non-inferiority conclusion. The study protocol specified a non-inferiority comparison of microbiological surveillance success between each functional-water system and the PAA-based system but did not specify a numerical non-inferiority margin. Therefore, the −5 percentage-point margin used in the present analysis was post hoc. A −10 percentage-point margin was additionally examined as an exploratory sensitivity analysis. Accordingly, inferences based on both numerical margins were considered exploratory. All evaluable endoscope-use episodes were included in the full analysis set. Surveillance success rates were summarized as proportions. Comparisons with the PAA-based group were expressed as risk differences in surveillance success with 95% confidence intervals calculated using the Newcombe method. Fisher’s exact test was performed descriptively. Subgroup and scope-level analyses were considered exploratory and were not adjusted for multiplicity because of the small number of surveillance failures. To address non-independence arising from repeated use of the same physical endoscope, post hoc sensitivity analyses were performed. A nonparametric cluster bootstrap used the anonymized physical-endoscope identifier as the resampling unit, retaining all endoscope-use episodes belonging to each resampled scope; 100,000 bootstrap replicates were used with random-number seed 20260812. In addition, a logistic generalized estimating equation model was fitted with physical endoscope as the clustering variable and an exchangeable working correlation structure. A further post hoc sensitivity analysis excluded all observations contributed by SCOPE005. These analyses were considered hypothesis-generating. Analyses were conducted using R (R Foundation for Statistical Computing, Vienna, Austria); the revised statistical code reproduces the primary and sensitivity analyses and records the R session information. Results Study cohort and procedural characteristics A total of 222 eligible endoscope-use episodes were randomized, with 74 allocated to each system. All 222 completed the assigned reprocessing procedure and microbiological sampling and were included in the analysis. A separate prospective screening log of endoscope-use episodes excluded before randomization was not maintained, so the total numbers screened and excluded before randomization could not be reconstructed reliably. The distribution of upper and lower gastrointestinal endoscope-use episodes was comparable across groups: 45 upper and 29 lower episodes in the strongly acidic electrolyzed-water group, 46 upper and 28 lower episodes in the ozonated-water group, and 45 upper and 29 lower episodes in the PAA-based group ( Table 1 ). Sampling was completed for all predefined sites in all analyzed episodes. Download: PNG larger image TIFF original image Table 1. Characteristics of endoscopes and procedural factors included in the study. https://doi.org/10.1371/journal.pone.0360048.t001 Mean age was 63.6 ± 11.0 years in the strongly acidic electrolyzed-water group, 62.1 ± 13.7 years in the ozonated-water group, and 64.4 ± 11.9 years in the PAA-based group; male sex accounted for 41/74 (55.4%), 47/74 (63.5%), and 47/74 (63.5%), respectively ( Table 1 ). Detailed diagnostic categories were not systematically collected for comparative analysis. Diagnostic examination only accounted for 50 (67.6%), 49 (66.2%), and 49 (66.2%) examinations, respectively. Biopsy was performed in 18 (24.3%), 14 (18.9%), and 16 (21.6%) examinations, and therapeutic intervention was performed in 6 (8.1%), 11 (14.9%), and 10 (13.5%) examinations, respectively. Biopsy and therapeutic intervention were not mutually exclusive; one PAA-group examination included both and was counted in both categories. Microbiological surveillance success Surveillance success was achieved in 67 of 74 endoscope-use epis
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