Setting and study population

UPMC Presbyterian Gastrointestinal Endoscopy service maintains a fleet of 26 duodenoscopes and 20 linear echoendoscopes to perform ∼1,000 endoscopic retrograde cholangiopancreatography and ∼1,000 EUS procedures annually. Specific devices may be temporarily or permanently replaced due to inspection, repair, or upgrade. The duodenoscopes in this analysis included model number TJF-180V (Olympus Medical Systems, Tokyo, Japan) prior to March 2021. These were subsequently and simultaneously all replaced with model number TJF-Q190V (Olympus Medical Systems), a device with a detachable and disposable tip (Fig. 1). The linear echoendoscopes were model number GF-UC140P-AL5 (Olympus Medical Systems).

Fig. 1.

Analysis periods for duodenoscope contamination, including by method of reprocessing, change to duodenoscope with disposable tip, and change from clinical to commercial laboratory. Note. dHLD, double high-level disinfection; HLD-ETO, high-level disinfection/ethylene oxide gas sterilization.

Reprocessing of duodenoscopes is performed in the gastrointestinal (GI) endoscopy laboratory by trained GI technicians according to the manufacturer’s instructions for use. The sequential steps of reprocessing are summarized as follows: (1) application of a pretreatment immediately after use (Pre-Klenz, Steris Healthcare, Mentor, OH); (2) visual inspection and manual cleaning (Prolystica, Steris Healthcare) using single-use brushes; (3) ultrasonic cleaning, detergent cleaning, rinsing, high level disinfection with acetic acid (5%), paracetic acid, hydrogen peroxide disinfectant (Acecide-C, Best Sanitizers, Penn Valley, CA); (4) rinsing, air purge, alcohol flushing, and a final air purge, all performed using an automated reprocessor (Olympus OER Olympus Medical Systems [Tokyo, Japan]); (5) drying for a minimum of 2 hours; and (6) storage in a facility-built, ventilated, closed cabinet.

Individuals performing reprocessing are trained by qualified experts and undergo competency re-evaluation annually. Quality control for automated disinfection is performed according to the manufacturer’s specifications; no deviations were noted during the study period. The quality of manual disinfection was verified using biologic sampling (ChannelCheck, Olympus, Tokyo, Japan); no failures occurred during the study period.

Reprocessing methods

Duodenoscopes and linear echoendoscopes undergo reprocessing as described above and are then wrapped in sterile blue packaging and delivered to the central processing department where ETO is performed (3M Ethylene Oxide Sterilization Monitoring, St. Paul, MN). After ETO sterilization, the scopes are returned in sterile packing to the GI laboratory where they are stored maintaining sterility. During a planned shutdown of the ETO sterilizer from June 16, 2020 through July 15, 2020, reprocessed duodenoscopes and linear echoendoscopes underwent a repeated cycle of HLD (ie, double HLD or dHLD) without removing the device from the reprocessor in place of ETO sterilization (Fig. 1).

Definitions

In this study, endoscope was defined as a unique duodenoscope and linear echoendoscope sampled 1 or more times. An endoscope culturing event was defined as obtaining a sample for culture from the instrument channel and elevator mechanism (or in few cases, either the instrument channel or elevator mechanism). This metric was the denominator for frequency of endoscope contamination. Sample site refers to either the instrument channel or elevator mechanism, and the sample refers to the specimen obtained from the instrument channel or the specimen obtained from the elevator mechanism. The resulting endoscope culturing event culture refers to the combined outcome for the instrument channel and elevator mechanism (eg, positive from 1 or both samples).

Outcomes

The primary outcome was the comparison of the pathogenic contamination rate identified from culturing events among endoscopes reprocessed by either dHLD or HLD-ETO. The coprimary outcome was the comparison of the pathogenic contamination rate between duodenoscopes and linear echoendoscopes processed by either reprocessing method.

Moreover, 5 secondary analyses were performed using the pathogenic contamination rate unless otherwise noted (eg, outcome of ≥1 pathogenic bacteria present in a sample of the elevator mechanism or instrument channel). We performed the primary analysis stratified by duodenoscopes and linear echoendoscopes type to assess effect modification by device type in the relationship between reprocessing method (HLD-ETO vs dHLD) and the frequency of contamination. Among duodenoscopes, we compared the frequency of contamination among standard model duodenoscopes and those with a detachable and disposable endoscope tip to determine whether this design modification resulted in a lower contamination rate. The primary outcome was compared to samples from the instrument channel and the elevator mechanism to understand the relative and independent contributions to duodenoscope contamination from these sampling sites. An analysis varying the outcome definition was performed to estimate the additional potential risk of endoscope contamination and transmission when fungal pathogens were considered in addition to bacterial pathogens. In these analyses, we qualitatively compared the primary analysis with alternate outcomes of pathogenic bacteria plus Candida spp and pathogenic bacteria plus any fungi. Lastly, we compared the frequency of the primary outcome among samples processed at a clinical microbiology laboratory versus a commercial environmental culture laboratory to validate the consistency of very similar microbiologic methods between these 2 laboratories. The change to a commercial laboratory occurred several months after dHLD use concluded (Fig. 1). Therefore, the comparison of outcomes between clinical and commercial laboratory processing was restricted to endoscopes reprocessed by HLD-ETO.

In a routine investigation, we followed a culture-positive endoscope (>1 CFU pathogenic bacteria or >10 CFU of any other bacteria or fungi). Endoscope use data were obtained from the automated reprocessor. Electronic health record review of patients who had a procedure with the affected endoscope within the prior 3 months or after the endoscope was last surveillance culture negative was performed to identify microbiologic laboratory findings with a culture matching or potentially matching the endoscope-cultured isolate. At the time of endoscope culture positivity, reprocessing practices were reviewed for potential breaches in reprocessing protocols, but none were found during this investigation.

Microbiologic methods

Samples were obtained for this study over a 15-month period from June 2020 through September 2021 (Fig. 1). Endoscopes were sampled after dHLD and drying or following ETO. As a quality assurance measure, we sampled every endoscope at least once per quarter and a minimum of 1 endoscope was cultured once each week based on the availability of the endoscope (ie, convenience sampling). The frequency of endoscope culturing increased to 3 culturing events per day, 4 days per week during the period when dHLD was performed in place of HLD-ETO for reprocessing

The sampling procedure was adapted from the FDA–CDC–ASM protocol ¹¹ with the following modifications: The elevator mechanism and instrument channel samples were processed separately. The use of alcohol swab and sampling of the external surface was omitted. The sample processing method was modified. The full sampling protocol is provided in the Supplementary Appendix (online). Sampling was performed by 2 people, including a trained infection prevention team member and GI technologist.

Prior to November 4, 2020, cultures were processed at a UPMC clinical laboratory, and after that time environmental cultures were processed in a commercial environmental sampling laboratory (Fig. 1). Summary microbiology methodologies for both laboratories are reported in the Supplementary Appendix (online). The gross contamination rate was defined as the number of endoscope cultures positive for growth of ≥1 colony-forming units (CFU) of ≥1 pathogenic organism or the growth of any bacteria or fungal organism in a quantity >10 CFU divided by the number of endoscopes cultured. The pathogenic contamination rate was defined as the number of endoscope cultures positive for the growth of ≥1 CFU of ≥1 pathogenic organism in either the elevator mechanism or instrument channel specimen divided by the number of endoscopes cultured. Pathogenic bacteria were defined as Enterobacteriaceae, Pseudomonas spp, Pantoea spp, Acinetobacter spp, Stenotrophomonas spp, Enterococcus spp, Streptococcus spp, and Staphylococcus aureus. ¹¹ As an additional analysis of the findings, the definition of pathogenic organism was modified in 2 ways: (1) this list of pathogenic bacteria or growth of Candida spp and (2) this list of pathogenic bacteria or any fungal growth. As part of our institutional guidelines, when an endoscope culture became positive with either >1 CFU pathogenic bacteria or >10 CFU of any other bacteria or fungi, the sampled endoscope was removed from use, reprocessed, and recultured before reuse. The repeated culture events were included in this analysis.

Statistical analysis

All data were collected using Excel (Microsoft, Redmond, WA), and statistical analyses were performed using Stata version 15.1 software (StataCorp, College Station, TX). Risk ratios were calculated (including 95% confidence intervals) for the coprimary outcomes of frequency of contamination between duodenoscopes and linear echoendoscopes and between reprocessing with dHLD versus HLD-ETO. The Pearson χ ² test of independence was used in the stratified analysis of frequency of contamination by endoscope type and reprocessing method. For all analyses, a P ≤ .05 was considered statistically significant. The remainder of comparisons to accomplish secondary aims were exploratory in nature, and no effect estimates or statistical tests of significance were derived. For this quality improvement investigation, the sample size was defined by the period the interventions were undertaken and endoscope sampling performed. This study was approved by the UPMC Quality Improvement Review Committee (project no. 2791).